1. ELECTROPLATING PLANT
Automatic Equipment
Fixed Sequence Automatic Plating Plant
Trojan and Gem Type Automatic Plant
Vulcan Lattice Arm Type Automatic Plant
Titan Type Automatic Plant
Digit Pivoted Arm Type Automatic Plant
Straight-through Type Automatic Plant
The Glydo System
Special Transporter Designs
Methods of Transporter Control
Programmed Controllers
Programme Preparation
Programming Systems
Photo-Electric Cell Type Reader
Microprocessor and Computer Control
Semi-Automatic Plating Plant
Barrel Planting Plant
Suitability of Articles for Barrel Plating
Barrel Types
Immersed Perforated Plating Barrels
Glydo/Glydette Barrel Plating Equipment
Horizontal Barrels
Barrel Perforations
Cathode Contacts
Current Control
Voltage
Speed of Barrels
Anodes
Types of Cathode Contacts
Calculation of Work Loads
Perforated Obliquc Barrels
Single Station Barrel Plating Units
Horizontal Barrels
Open-ended Plating Barrels
Manual Planting Plant
Modular Plant and Specialised Equipment for the Electronics Industry
Uniplan
Uniplan Barrel Plating
2. ELECTROPLATING EQUIPMENT
Process Tanks
Welded Steel Tanks
Plastic Tanks
Plastic Tanks Reinforced with Glass Fibre
Glass Fibre (GRP) Tanks
Stainless Steel
Tank Lining Materials
Rubber
Treatment of Rubber Linings
Key to Table
Polyvinyl Chloride
Ilex Grade Plastic Lined Tanks
Lead
Materials of Construction—Containers, Hooks, Dipping Baskets
Aluminium
Glass
Brass, Bronze and Copper
Monel Metal
Nichrome (‘Chrome’ Wire)
Rods & Connections for Process Tanks
Solution Heating
Stem Heating
Steam Coils
Plain Steel Coils
Galvanised Steel Coils
Lead and Lead Alloy Coils
Titanium Coils
Zirconium Coils
Tantalum Coils
Incoloy 825 Coils
Stainless Steel Coils
Fluorocarbon Coils (Dupont Teflon Heat Exchangers)
External Heat Exchangers
Water Jackets
High and Medium Pressure Hot Water Heating
Liquid Phase Heating
Gas Heating
Electric Heating
Metal Cased Heaters
Teflon Immersion Heaters
Silica Cased Heaters
Earthing of Electrically Heated Tanks
Electric Heating of Plastic or Plastic Lined Tanks
Solution Level Control
Lagging and Heat Conservation
Chroffles
Calculation of Heating Requirements
Allowance for Heating Losses
Steam Boilers
Hot Water Boilers
Gas Heating
Electric Heating
Temperature Control
Temperature Indicators
Thermostatic Control Equipment
Solution Cooling
Solution Agitation
Air Agitation
Mechanical Work Movement
Fume Extraction and Shop Ventilation
Fume Scrubbers and Demisters
Filtration of Solutions
Sentinel Filter Units
Sieber Filter Units
Hendor Filter Units
Solution Circulation and Transfer
Filter Media & Filter Aids
Filter Media
Filter Aids
Pumps for Pressure Filtration
Pipework for Filtration
The Drying of Components
Centrifugal Dryers
Automated Centrifuge Units
Hot Air Ovens
Hot Sawdust and Grit-o-cobs
Jigs & Racks For Electroplating, Anodising and Other Surface Coatings and Treatments
Plating Jig Design
Jig Contacts
Anodising Jigs
Jig Insulation
Safety Precautions
Ohmax Coating Procedure
Equipment
Maintenance
Removal of the Insulated Coatings
3. ELECTRICAL EQUIPMENT
Rectifiers Rectifier Rating
Rectifier Installation and Maintenance
Single Phase Rectifier Units
Rectifier Control
Auto-transformers
Stepless Regulators
Thyristor controlled rectifiers
Constant Voltage and Constant Current Control
Controllers for Anodic Oxidation Processes
Automatic Control
Current Interrupters and Periodic Reverse Units
Periodic Control Units for use with separate rectifiers
Electrical Instruments
Ammeters
Voltmeters
Ampere Time Meters
Pre-setting Ampere-time Meters and Panels
Heavy Current DC Switch-gear
Connecting Up Plating Equipment
D.C. Wiring Systems
Busbars
Busbar Ratings
Busbar supports
Jointing with flat busbars
Copper Rod and Flexible Conductors
4. CLEANING, PICKLING AND DIPPING
Routine Operations in Cleaning
Preliminary Cleaning and Degreasing
Solvent Cleaning
Aqueous Neutral Detergent Pre-Cleaners
Mersol Soak Cleaner
Solution Composition
Solution Preparation
Operating Conditions
Operating Procedure
Ultrasonic Cleaning
Alkaline Cleaners
Hot Alkaline Cleaners
Classification of Metal Cleaners
Electrolytic Cleaning
Equipment for Hot Alkaline Cleaners
Barrel Cleaning
Activax Cleaner
Equipment
Solution Preparation
Solution Concentration and Operating Conditions
Cleaning of Zinc Base Alloy Die Castings
Barrel Cleaning
Solution Maintenance
Nuvax Cleaner
Equipment
Solution Preparation
Cleaning of Zinc Base Alloy Die Castings
Barrel Cleaning
Solution Concentration and Operating Conditions
Solution Maintenance
Cleaner
Equipment
Solution Preparation
Solution Concentration and Operating Conditions
Solution Maintenance
Multiklense
Equipment
Solution Preparation
Solution Maintenance
Cleaner No. 50
Solution Concentration and Operating Conditions
Solution Composition
Solution Preparation
Operating Conditions
Solution Maintenance
Anozyn
Equipment
Solution Composition
Solution Preparation
Operating Conditions
Solution Maintenance
10-15 Cleaner
Equipment
Solution Concentration and Operating Conditions
Solution Preparation
Solution Maintenance
10-55 Cleaner
Equipment
Solution Preparation
Operating Conditions
Solution Maintenance
Emphax
Equipment
Solution Composition
Operating Conditions
Solution Maintenance
Zonax Metal Cleaner
Solution Concentration and Operating Conditions
Anodax Metal Cleaner
Equipment
Solution Composition
Solution Preparation
Operating Conditions
Solution Maintenance
Alkaline Cleaners for Aluminium
For Cleaning without Etching the Surface
For Light Etch Cleaning of Aluminium
For Frosted Etch Finish
Minco Cleaner
Equipment
Solution Concentration and Operating Conditions
Solution Maintenance
Kelco Cleaner
Equipment
Solution Composition
Solution Preparation
Operating Conditions and Procedure
Solution Maintenance
Maintenance of Metal Cleaners
Additions of Metal Cleaner
Pickling and Dipping
Zonax Dry Acid Salt
Equipment
Solution Concentration and Operating Conditions
Solution Preparation
Sulphuric Acid Pickling
Equipment
Solution Composition
Operating Conditions
Solution Maintenance
Hydrochloric Acid Pickling
Solution Composition
Equipment
Operating Procedure
Skalene Pickle for Iron and Steel
Alkaline Deruster Salts
Additional Uses of Alkaline Deruster Salts
Equipment
Section A—Cyanide-free Solution for Rust Removal
Solution Composition
Solution Preparation
Operating Conditions
Section B.—Cyanide Solution for Rust and Scale Removal
Solution Composition
Operating Conditions
Process Sequence used in Sections A and B
Treatment of High Tensile Steels
Spray Suppression
Effluent Treatment
Solution Maintenance
Hydrofluoric Acid Pickling
Solution Composition
Equipment
Operating Procedure
Pickling of Magnesium Alloys
Pickling of Stainless Steel
Equipment
Operating Procedure
Pickle Aid
For Combined Pickling and Degreasing Solutions
As a Spray Suppressant
Equipment
Concentration
Operating Conditions
Solution Maintenance
Bright Dipping of Copper Alloys
Aqua Fortis Bright Dipping Acid
Solution Composition
Equipment
Bright Dipping Procedure
Chromic Acid Dip for Brass, Copper and its Alloys
Solution Composition
Equipment
Operating Procedure
Nitric Free Bright Dip C22924 for Copper and its Alloys
Solution Composition
Equipment
Operating Procedure
Solution Maintenance
Barrel Pickling
Second Stage or Surface Activation Cleaning
Cyanide Containing Cleaners
Klenewell
Equipment
Solution Composition
Solution Preparation
Operating Conditions
Operating Procedure
Solution Maintenance
Kleenax
Solution Concentration
Operating Conditions
Operating Procedure
Solution Maintenance
Non-Cyanide Cleaners
Activax Cleaner
10-55 Cleaner and Anodax Metal Cleaner
Anozyn
Alkaline Deruster
Emphax Cleaner
Acid Etching
Anodic Sulphuric Acid Etching of Iron and Steel
High Concentration Acid Etch for Steel
Equipment
Solution Composition
Solution Preparation
Operating Conditions
Operating Procedure
Solution Maintenance
Acid Etching of Steel and Iron before Heavy Deposition
Solution Composition
Solution Preparation
Operating Conditions
Solution Maintenance
Pre-Treatment Systems
Pre-Cleaning
Typical Cleaning Cycles
Nickel Plating of Mild Steel
General Method
Where a cyanide-free cleaning line is required
Use of a sulphuric acid etch to ensure maximum adhesion of deposit
D.—Energy Saving Cleaning Line
Cadmium and Zinc Plating of Mild Steel
Rack Plating
Notes
Barrel Plating
Notes
Plating on High Carbon Steel
Plating on Cast Iron and Malleable Castings
Plating on Stainless Steel
Nickel Chloride Strike for Stainless Steel
Nickel Sulphate Strike for Stainless Steel
Nickel Plating of Brass and Other Copper Alloys
General Method
Alternative method where a cyanide-free cleaning line is required
Nickel Plating of Copper
Nickel Plating of Leaded Brass
Copper and Nickel Plating on Zinc Base Alloy Die-Castings
Plating on Aluminium and its Alloys
The Bondal Process
Bondal Cleaner
Equipment
Solution Composition
Solution Preparation
Operating conditions
Solution Maintenance
Bondal Dip
Standard process sequence for electro-plating on
aluminium and its alloys
Modification to the standard process
Articles likely to carry over solution
Articles having unpolished areas
Deposition of metals other than nickel
Jigging
Dips and Rinses
Dilute Acid Dips
Cyanide Dips
Rinsing or Swilling
Rinse-Aid
Scouring
5. ELECTROLYTIC AND CHEMICAL PROCESSES FOR THE POLISHING OF METALS
Electro-polishing Solutions
Aluminium and Aluminium Alloys
Aluminium Electro-polishing Solution
Equipment
Solution Composition
Solution Preparation
Operating Conditions
Operating Procedure
Solution Maintenance
Brytal Process
Equipment
Operating Conditions
Desmutting
Stainless Steels
Canning Stainless Steel Electro-polishing Solution
Solution Composition
Equipment
Operating Conditions
Process Sequence
Solution Maintenance
Copper, Brass and Nickel Silver
Canning Non-Ferrous Electro-polishing Solution
Solution Composition
Equipment
Operating Conditions
Process Sequence
Solution Maintenance
Chemical Polishing of Aluminium
Typical Operating Conditions
6. COPPER PLATING
Properties of Copper
Decorative Applications
Functional Applications
Copper Plating Solutions
Rates of Deposition and Specification Requirements
Cathode Efficiency of Copper Plating Solutions
Rates of Deposition
Deposit Specifications
Equipment
Cyanide Solutions
Anodes
Cyanide Copper Plating Processes
Copper Strikes
pH Control
Cuprax High Efficiency Copper Solution
Anodes
Solution Composition
Operating Conditions
Solution Maintenance
Purification
Analytical Standards
Plating Procedure for Zinc based diecastings
Zonax Copper Solution
Anodes
Solution Composition
Operating Conditions
Maintenance of the Solutions
Low Cyanide Strike Solution for Cast Iron, Lead and Soldered Articles
Analytical Standards
Rochelle Copper Solution
Solution Composition
Operating Conditions
Solution Maintenance
Analytical Standards
Acid Copper Plating Processes
Cuprasol Mk 2 Bright Levelling Acid Copper Plating Sollution
Preparation of the Cuprasol Mk. 2 Base Solution
Solution Composition
Operating Conditions
Solution Maintenance
Chloride Content
Visual Control of the Cuprasol Solution
Acid Copper Sulphate Solution
Solution Compositions
Operating Conditions
Solution Maintenance
Correction of Faults in Acid Copper Sulphate Solutions
Copper Pyrophosphate Plating Solution
Super Pyrobrite Copper Pyrophosphate Plating Solution
Solution Composition
Solution Maintenance
Plating Procedure
Neutral Copper Plating Solutions
Solution Composition
Operating Conditions
Plating Procedure
Immersion Plating Without Applied Current
On Steel
Solution Composition
On Brass
Solution for Barrel Copper Plating
Barrel Plating with Zonax Copper Solution
Solution Compositions
Operating Conditions
Maintenance of Solutions
Analytical Standards
Barrel Plating With Cuprax Copper Solution
Solution Composition
Operating Conditions
Solution Maintenance
Analytical Standards
BarRel Plating in Rochelle Copper Solution
Operating Conditions
Analytical Standards
Solutions for Heavy Copper Deposition
Cuprasol Mk. 2 Acid Copper Plating Process for Heavy Deposits
Preparation of the Acid Copper Base Solution
Solution Composition
Operating Conditions
Solution Maintenance
Analytical Standards
Copper Fluoborate Solution
Equipment
Operating Conditions
Solution Maintenance
Purification
Analytical Standards
Super Pyrobrite Copper Pyrophosphate Plating Solution
Properties of the deposit
Operating Conditions
Purification
Cuprax Cyanide Copper Solution
Copper Plating Procedure
Cyanide Copper Solutions
Zinc Base Alloy Diecastings
Special Techniques used in Printing Application
Photogravure
Building Up Copper Cylinders
Skin Deposits
Cast Iron and Steel Cylinders
Aluminium Cylinders
Copper Electrotypes
Lithography
Stopping-Off
Methods for Stripping Copper Deposits
From Steel
Universal Stripping Salts for Steel
Alkaline Cyanide Solution
Immersion Process
Sulphuric Acid Etch
From Zinc Alloy Diecastings
7. ELECTROFORMING
Applications of Electroforming
Materials for Electroforming
Nickel Solution
The Watts Solution
The Sulphamate Solution
The Ni-spoed Solution
Zero-stress conditions for the Ni-speed process
Nickel/Cobalt Alloy Solutions
Copper Plating Solution
Throwing power
Sodium High-Sulphate Nickel Solution
Operating Techniques
Mandrels for Electroforms
Permanent Mandrels
Stainless steel
Mild Steel
Copper and Brass
Electroformed Nickel
Rigid Plastic
Collapsible Plastics
Expendable Mandrels
Aluminium
Zinc alloys
Fusible alloys
Plastics
Wax
Other Materials
Post Plating Treatment
Electroforming in Gramophone Record Production
Printing Application
Printing Methods
Electroplating Techniques Special to the Printing Industry
Electroplating Solutions used in the Printing Industry
8. BRASS PLATING
Decorative Brass Plating
Zonax Brass Solution for Decorative and General Plating
Equipment
Solution Composition
Operating Conditions
Solution Maintenance
Colour Consistency and Control
Analytical Standards
Plating Procedure
Brass Plating upon Cast Iron and Lead
Barrel Brass Plating
Solution Composition
Operating Conditions
Solution Maintenance
Analytical Standards
Brass Plating for Rubber Adhesion
Solution Composition
Operating Conditions
Solution Maintenance
Analytical Standards
Plating Procedure
Correction of Faults in Zonax Brass Plating Solutions.
9. SILVER PLATING
Cyanides Systems
High-Speed Selective Plating
Non-cyanide System
Iodide Solutions
Trimetaphosphate Solution
Thiosulfate Solutions
Succinimide Solutions
Organic Solvent Solutions
Summary
Tin, Lead, and Tin-Lead Plating
Additives
Tin, Lead, and Tin-Lead Plating Baths
Tin Barrel, Still, and High-Speed Baths
Lead Barrel and Still Baths
60 Tin/40 Lead Solder Barrel, Still, and High-Speed Baths
90 Tin/10 Lead Barrel, Still, and High-Speed Baths
93 Lead/7 Tin Barrel and Still Baths
10 Tin/88 Lead/2 Copper Ternary Alloy Barrel and Still Baths
Fluoborate Plating
Methane-Sulfonic-Acid-Based Plating
Tin Plating From Stannate Baths
Anodes in Stannate Baths
Operation of Stannate Baths
Reflowing Tin Deposits
Determination of Acid Neutralization Value
10. TIN-NICKEL ALLOY PLATING
Properties and Applications
The Plating Baths
Chloride-Fluoride Baths
Chloride-Fluoride Solution Preparation
Solution Agitation
Anodes
Effects of Process Variables
Effects of Solution Contaminants
Table 4. Solution Composition and Control Limits for Pyrophosphate-Glycine Bath
Pyrophosphate-Glycine Bath
Troubleshooting Guidelines
11. GOLD PLATING (GILDING)
Properties of Gold
History of Gold Plating
Applications of Gold Plating
Rates of Deposition and Specification Requirements
Specification Requirements
Undercoats
Corrosion Resistance
Carat Value
Equipment for Gold Plating
Anodes
Effluent Treatment
Gold Deposits and Solutions
Ultra-pure Gold Deposits
Low-Alloy Gold Deposits
High-Alloy Decorative Golds
General Gold Plating Procedure
Plated Undercoats
Barrier Layers
Strike solutions
Post plating treatment
Traditional Gold Plating Practice (Gilding)
Gilding Articles Inside
Immersion Gilding
Stripping Gold Deposits
Electrolytic Process for Stripping Flux and Oxide from Gold
12. CADMIUM PLATING
Properties of Cadmium
Applications and Corrosion Resistance
Cadmium Deposits on Non Ferrous Metals
Passivation Processes
Specification Requirements and Rates of Deposition
Rates of Deposition and Plating Times
Determination of Deposits Thikness
Strip and re-weigh method for average thickness of cadmium deposits
Test for Porosity of Deposit
Cadmium Plating Equipment
Cadmium Plating Solutions
Cadmium Plating Salts
Zonax Candmium Plating Solution
Solution Composition
Operating Conditions
Solution Maintenance
Analytical Standards
Kadax Cadmium Solution for Barrel Plating
Solution Composition
Operating Conditions.
Solution Maintenance
Analytical Standards
Kadamax High Speed Bright Cadmium Plating Solution
Equipment
Solution Composition
Operating Conditions
Solution Maintenance
Analytical Standards
Cadmium Plating Procedure
Cleaning and Preparation of Work
Removal of Embrittlement
Treatment after Cadmium Plating
Kadip Bright Dip
Equipment
Solution Composition
Operating Conditions
Solution Maintenance
Chromic Acid Dip
Equipment
Solution Composition
Operating Conditions
Stripping Cadmium Deposits
Using Ammonium Nitrate Solution
Using Ammoniacal Persulphate Solution
Using Hydrochloric Acid
13. ZINC PLATING
Properties of Zinc
Applications Corrosion Resistance
Specification Requirements and Rates of Deposition
Thickness Requirements for Zinc Deposits
Determination of Thickness of Zinc Deposit
Rate of Deposition
Zinc Plating Equipment
Cyanide solutions
Zinc Plating Solution
Cyanide Zinc Plating Solutions
Base Solution Composition
Unizin Universal Zinc Brightner
Anodes
Solution Composition
Operating Conditions
Solution Maintenance
Analytical Standards
Purification
Hylite 80 Bright Zinc Solutions
Solution Composition
Operating Conditions
Solution Maintenance
Zinc Oxide
Zinc Cyanide
Purification
Analytical Standards
Treatment after Plating
Cyanide Zinc Plating Procedure
Cleaning and Preparation of Work
Treatment After Zinc Plating
Bright Zinc Plating
Dilute Nitric Acid Bright Dip
Dull Zinc Plating
Correction of Faults In Cyanide Zinc Plating Solutions
Alkaline Non-Cyanide Zinc Solutions
Envirozin 2 Bright Alkaline Non-Cyanide Solution
Solution Composition: Rack
Solution Composition: Barrel
Solution Preparation
Operating Conditions
Rate of Deposition
Solution Maintenance
Analytical Standards
Purification
Alkaline Non-Cyanide Plating Procedure
Acid Zinc Plating Solutions
Zincalux Bright Acid Zinc Solution
Solution Composition
Operating Conditions
Rate of Deposition
Solution Maintenance
Purification
Analytical Standards
Treatment after Plating
Chloride Zinc Plating Solution
Equipment
Solution Composition
Operating Conditions
Rate of Deposition
Solution Maintenance
Treatment of Work after Plating
Acid Zinc Plating Procedure
Stopping-off
Stripping Zinc Deposits
Immersion Process
Correction of Faults in Acid Chloride Zinc Plating Solutions
Electrolytic Process
14. PASSIVATION PROCESSES FOR ZINC AND
CADMIUM ELECTRODEPOSITS
Drying
Passivation Processes For Zinc and Cadmium
Full Passivation Processes
Zonax Passivating Salts
Equipment
Solution Composition
Operating Conditions
Process Sequence
Solution Maintenance
Chromate Passivation Solution To D.E.F. 130
Equipment
Solution Composition
Operating Conditions
Process Sequence
Analytical Standards
Solution Maintenance
Autopass Salts
Equipment
Solution Composition
Operating Conditions
Process Sequence
Solution Maintenance
Production of Blue Chromate Coating
Full Passivation Concentrate
Equipment
Solution Composition
Operating Conditions
Process Sequence
Solution Maintenance
Production of Blue Chromate Coating
Heavy Bronze Passivation
Solution Composition
Operation Conditions
Process Sequence
Solution Maintenance
Black Chromate Passivation For Zinc
Solution Composition
Operating Conditions
Process Sequence
Solution Maintenance
Olive Drab Chromate Passivation
Solution Composition
Operating Conditions
Process Sequence
Solution Maintenance
Black Finish
Light, Colourless or Blue Passivation Process
Blue Passivating Salts For Zinc
Equipment
Solution Composition
Operating Conditions
Process Sequence
Solution Maintenance
Bright Passivation For Zinc
Solution Composition
Operating Conditions
Process Sequence
Solution Maintenance
Zinc Chromate Passivation
Equipment
Solution Composition
Operating Conditions
Process Sequence
Solution Maintenance
Iridex
Colourless Passivation on Cadmium
Equipment
Solution Composition
Operating Conditions
Coloured Finishes
Black Dye for Olive Drab Passivation
Blue Identidye
Equipment
Operating Sequences
Test Procedure For Passivated Films
Spot Test Solution for Chromate Passivation Films
15. THE PLATING OF PLASTICS AND OTHER
NON-METALLIC MATERIALS
Plating-on-Plastics
Applications and Advantages
Properties of Plated Plastics
Moulding for Plating on Plastics
Physical faults and their effects
Faults caused by variations in machine parameters
Simplas Process
Equipment
Swilling or Rinsing
Cleaning
Pre-etch
Hot Alkaline Cleaner
Etching
Etch Composition for ABS Type Polymers
Operating Conditions
Solution Maintenance
Analytical Standards
Etch Composition: For PP co-polymers
†Alternatives:
Operating Conditions
Solution Maintenance
Analytical Standards
Neutralising
Solution Composition
Solution Maintenance
Simplas Neutraliser
Solution Composition
Operating Conditions
Activation
Solution Composition
Operating Conditions
Solution Maintenance
Acceleration
Solution Composition
Operating Conditions
Niplas Electroless Nickel
Equipment
Solution Composition
Operating Conditions
Solution Maintenance
Solution Life
Analytical Standards
Electroplating on Electroless Nickel Plated Surfaces
Plating Jigs
Barrel Plating of Plastics
Barrel Plating Technique
Silvering
Spray Silvering
Solution Composition
Operating Procedure
Sensitiser
Immersion Silvering
Operating Procedure
Electroplating on Silvered Surfaces
Jigging
Special Techniques Used In Printing Applications
Metallising with Copper Bronze Powder
Preparation
Metallising
Electroplating
Polishing with Powered Graphite
Vacuum Evaporation and Electrical Sputtering
16. PLATING FOR ELECTRONICS
Printed Circuits
Specialist Processes for Printed Circuit Production
Print and Etch Circuits
Applying the Resist
Producing the Circuit Pattern
Etching
Finishing
Plated Through Hole Circuits
Drilling
Pretreatment
Additive Circuitry
Semi-Additive circuits
Fully Additive Circuits
Gold Plating of Edge Connectors
65 Copper Etchant For Printed Circuits
Equipment
Solution Composition
Operating Conditions
Solution Maintenance
Analysis of 65 Copper Etchant
Estimation of Hydrogen Peroxide in Bath
Estimation of Copper in Bath
Copper Recovery
P.D. Activator for Printed Circuits
Solution Composition
Operating Conditions
Cuprasol PTH Copper Plating Process
Equipment
Solution Composition
Operating Conditions
Preparation of Cuprasol PTH Base Solution
Solution Preparation
Analytical Standards
PTH Tin/Lead Plating Solution
Equipment
Solution Composition
Operating Conditions
Solution Maintenance
Analytical Standards
Dekote PB/SN 1
Equipment
Solution Composition
Operating Conditions
Operating Procedure
Solution Maintenance
Dekote Au
Equipment
Solution Composition
Operating Conditions
Operating Procedure
Solution Maintenance
17. PHOSPHATING PROCESSES
Applications
Pre-treatment Prior to Organic Coatings
Protection against Corrosion
Anti-wear Coatings
Phosphating as a Production Aid
Types of Phosphate Coating
Iron Phosphate
Zinc Phosphate
Manganese Phosphate
Lead Phosphate
Surfaces To Which Phosphate Coatings May Be Applied
Preparation of Surfaces for Phosphating
Specifications
British Standard 1389: 1973 Phosphate Treatment of Iron and Steel
DEF STAN 03-11/1 Phosphate Treatment of Iron and Steel
Treatment of High Tensile Steels
Equipment for Phosphating
Immersion Phosphating Plant
Spray PhospHating Equipment
Tanks
Solution Heating
Fume Extraction
Sludge Removal
Phosphating Processes
Key to Table
Light Weight Iron Phosphate Processes
Canphos 301
Canphos 304
Equipment
Solution Composition and Operating Conditions
Preparation of the 300 Range Phosphating Solutions
Operating Sequences
Solution Maintenance
Heavy Zinc Phosphate Processes
Equipment
Canphos 401
Canphos 402
Solution Composition and Operating Conditions
Preparation of the 400 Range of Phosphating Solutions
Solution Maintenance
Visual Control
Calcium Modified Zinc Phosphate Processes
Canphos 501
Canphos 504
Canphos 509
Equipment
Solution Preparation
Operating Sequences
Solution Maintenance
Addition Rates
Light Weight Zinc Phosphate Processes
Canphos 505
Canphos 508
Solution Composition and Operating Conditions
Solution Preparation
Solution Maintenance
Addition Rates
ManganEsE Phosphate Processes
Canphos 601
Equipment
Solution Composition
Operating Conditions
Solution Preparation
Operating Sequences
Solution Maintenance
Phosphating Process Sequences
Pre-Treatment Processes
Alkaline Cleaners
Equipment
Maintenance
Defoaming
Pickling and Derusting
Conditioning
Post Phosphating Treatments
Sealing Treatment
Chromic Rinse Solution (DEF STAN 03-11/1)
Equipment
Oils and Lubricants
Black Finishes
Sealphos 721 Black Stain
Sealphos 708 Matt Black
Aluminium Pre-Treatment
Alibond 802
Equipment
Solution Composition
Operating Conditions
Operating Sequence
Solution Maintenance
Solution Analysis
General Phosphating Information
Sludge Removal
Control of Solution Composition and Chemical Balance
Effluent Treatment
18. CHEMICAL FINISHING OF ALUMINIUM
Introduction
Etching
Alkaline Etching
Acid Etching
On-Site Etching
Bright Etching
Chemical Brightening
Electorbrightening
19. ELECTROPLATING ON ALUMINIUM
Background To Plating
Advantages of Electroplating Aluminium
Examples of Electroplated Aluminium
Alloys for Plating
Processing
Early Pre-treatment Methods
Preplating Procedures
1 Polishing
2 Jigging
3 Cleaning
4 De-smut
5 Pre-treatment
Electrodeposition
20. CHEMICAL COLOURING OF ALUMINIUM
Introduction
Conversion Coatings
Thickened Oxide Coatings
21. ELECTROPAINTING OF ALUMINIUM
The Process
Principles of Electropainting
Process Details
Jigging
Pre-treatment
Paint Application
4 Rinsing and Ultrafiltration
Stoving
Costs
Conclusion
Developments
The Future
22. POWDER COATING OF ALUMINIUM
Method of Application
Equipment
Electrostatic Generator and Gun
Powder Recovery
Stoving
Powder Coating Production
Colour
Thermoplastic Powder Coatings
Polyethylene (Polythene)
PVC
Nylon
Factors Affecting Use of Thermo-plastic Coatings
23. BRIGHT NICKEL ELECTRO-PLATING
Brighteners
Levellers
Stress Relievers
Wetting Agents
Properties of electro-deposited bright nickel
Brightness
Reflectivity
Roughness and Pitting
Porosity
Corrosion Resistance
Chromability
Adhesion and Surface Preparation
Ductility
Internal Stress
Hardness
Effect of hydrogen absorption
Properties of Bright Nickel Baths
Stability
Cathode and anode efficiencies
Operating range
Simplicity of operation
Throwing power
The incorporation and effect of organic addition agents
Mechanisms of incorporation of organic compounds in electro-deposits
Cathodic Reduction
Interaction of organic additions
Levelling
Effect of additives on structure
Grain size, orientation and brightness of electro-deposits
Effect of additions on stress, ductility and hardness
Stress first decreases, then rises as concentration is increased.
24. ELECTROPLATING SOLUTIONS
Brass and Bronze Plating
White Brass
Bronze Plating
Cadmium Electro-plating
Alkaline Cyanide Baths
Preparation of the Plating Bath
Production Plating Conditions
Acid Sulfate Baths
Preparation of the Plating Bath
Production Plating Conditions
Neutral Chloride Baths
Preparation of the Plating Bath
Production Plating Conditions
Acid Fluoborate Baths
25. DECORATIVE CHROMIUM PLATING
Chemistry for Hexavalent Chromium
Chemistry—Trivalent Chromium
Operations
Equipment
Waste Treatment
Corrosion Protection
Decorative Black Chromium
Bulk Chromium Plating
26. FUNCTIONAL CHROMIUM PLATING
Chemistry
Operating Conditions
Power Supply
Anodes
Fixturing and Rack Design
Stop Offs
Tapes
Lacquers
Wax
Shields and Robbers
Specialty Chromium Baths
Trivalent Chromium
Black Chromium
Porous Chromium
Environmental Concerns
Air Handling
Impurity Removal From a Plating Bath
Regulations
27. COPPER PLATING
Copper Cyanide Baths
General Purpose Strike
Strike-Plate Bath
High-Efficiency Bath
Barrel Plating
Bath Preparation
Maintenance and Control
Constituents
Temperature
Agitation
Contamination
Carbonate
Copper Pyrophosphate Plating Baths
Strike
Typical Pyrophosphate Bath
Printed Circuit Bath
Maintenance and Control
Constituents
Temperature
Agitation
Contaminants
Orthophosphate
Other Alkaline Baths
Copper Sulfate Baths
Standard Acid Copper Plating
High-Throw Bath
Bath Preparation
Maintenance and Control
Constituents
Temperature
Agitation
Contaminants
Copper Fluoborate Bath
Maintenance and Control
28. GOLD PLATING
Decorative Gold Plating (Classes A—C and, sometimes, G)
Barrel Plating (Classes A and B)
Antique Golds (Classes A and B)
Heavy Decorative Gold (Classes C-1 and C-2)
Industrial/Electronic Gold Plating
Alkaline Cyanide Baths (Group 1, Class D)    
Neutral Cyanide Solutions (Group 2, Class D)
Acid Cyanide Plating Solutions (Group 3, Class E)

Directory Section

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Electroplating Plant

Automatic Equipment

Mechanization has been applied to the electroplating process since the 1920’s, but until the I960’s its use was restricted to those organizations having massive quantities of components of similar type and which required an identical finish. In the last decade there has been a complete change in the situation with mechanization or automation being applied on an ever extending scale.

Today, any electroplating production or output requirement from the mass production demands of the automobile industry to the small scale needs of the electronics manufacturer may be met and variations in the components to be processed and in the specification requirement are no longer an obstacle to the employment of automatic handling techniques.

An automatic electroplating plant is essentially a line of process tanks with a transfer system, which enables the articles to be electroplated to be immersed in each tank for the appropriate time and in the sequence necessary to produce the required finish.

Automatic electroplating equipment may be divided into two groups:

Fixed sequence plant, which is the subject of the next section of this chapter, is employed where large volumes of work of a similar type are processed.

Variable programme plant, which incorporates one or more independent transporters (lift/traverse units) operating under the instruction of a programmed controller.

Fixed Sequence Automatic Plating Plant

The first automatic plant was essentially a development of the conveyor system in order to provide:

       1.  Immersion times in different tanks over a wide time scale.

       2.  Rapid inter-tank transfer to avoid staining of the work.

In the early 1950’s, the conventional automatic plating plant developed on the basis of a return type design with a centre lifting carriage around which the tanks were arranged in a U formation. For large outputs and for the most effective use of floor space, this type of equipment is still to be preferred. It is however, subject to limitations in that, these designs can only be considered when there is a fairly narrow range of components to be processed and there is a common specification requirement. In general, the equipment is restricted to the single process sequence for which the plant was designed and whilst the speed of operation can be varied, such a change will introduce a proportional change in the immersion times at every other stage in the process sequence.

Within the well proven designs of the fixed sequence automatic electro­plating plant, efforts have been made to introduce a degree of variability so that this type of equipment could be employed where there are alternative specification requirements, for example, differing types of passivation on zinc deposits; a number of deposit thickness requirements or differing types of coating to be applied.

Equipment of this type includes the Trojan. Gem, Titan, Vulcan and Digit ranges of automatic plant.

A number of different mechanical transfer systems are employed which may be hydraulic or electromechanical in operation. The choice of system is dependent upon the output, the jig load and the process requirements.

The majority of automatics are of the return type with the load and un­load positions adjacent. This arrangement makes economical use of the lifting mechanism and also enables the plant to be operated from a single position.

Trojan and Gem Type Automatic Plant

With these automatics hydraulic power is employed to operate both the lift and traverse movements, and the use of unit type construction permits plant modification should it be necessary to alter the process sequence at a later date.

The plant is made up of a series of tanks. For processes requiring a short immersion time, e.g. water rinses and acid dips, single station tanks which will accommodate one work arm are used. For processes requiring a longer immersion time, e.g. electroplating, multi-station tanks are used which will accommodate a number of work arms. On these tanks, the jigs carried by the work arms progress through from one end of the tank to the other, remaining immersed for the required process time.

The basic sequence of movement is:

    Lift

    Upper traverse

    Lower

    Bottom traverse

    Dwell.

During the ‘dwell’ period, the plant is stationary. The ‘dwell’ time is generally 30 to 60 seconds, which, with the normal transfer time of 30 seconds, would give an average throughput of 40 to 60 work arms per hour. On the Gem type plant, one jig per work arm is the usual, whilst on the Trojan automatic each work arm carries two jigs. The ‘dwell’ period is controlled by means of an electronic timer and can thus be readily adjusted.

The tracks on which the work arms are carried are divided into fixed and lifting sections. On single station tanks, the track is a lifting section attached to the carriage. On multi-station tanks, the initial and final sections of the track lift, but the centre section is fixed so that on this section the jigs remain in the solution during the lifting cycles, and are progressed forward at each lower traverse movement.

The lift to the carriage is provided by a number of single acting hydraulic cylinders base mounted and synchronized by means of racks and pinions linked by a line shaft. The cylinders provide the support for the lifting carriage, thus avoiding the need for an overhead framework.

The traverse movement is by means of reciprocating pushers operated by two or four hydraulic cylinders.

The pushers are pivoted on the reciprocating traverse bars so that they may be lifted clear of the work arms on the return stroke and also during the lower traverse movement at single station tanks where no forward movement is required.

Vulcan Lattice Arm Type Automatic Plant

The lattice arm type automatic is used where the loads on the work arm are high and also where deep process tanks are employed, which necessitate a long lifting movement.

The transfer system consists of a number of vertical slides, in which the work arms are carried, the slides being linked by upper and lower driving chains. The vertical lift movement is by means of an internal carriage provided with hydraulic or mechanical lifting gear. Lattice arm type plant may be fitted with ‘delayed set-down’ to permit very short immersion times at selected process stages and also ‘skip’ by which a particular stage or stages can be missed with the work carriers held above solution level, whilst the carriage descends. This permits process variation and also the storage of plating jigs on the plant. The incorporation of a storage track at the upper level enables jigs to be loaded on to the plant at the end of a shift in preparation for the next production run.

Titan Type Automatic Plant

This type of automatic differs from the Trojan and Gem in that separate upper and lower traverse mechanisms are provided, with the upper traverse gear curried on overhead framework. The Titan may be used where the jig loading is greater than that permissible with the Trojan.

Digit Pivoted Arm Type Automatic Plant

This represents the simplest form of transfer system with the lifting movements being provided by a cam track along which the work arms travel. The Digit type plant is suitable for light work and small area jigs. See illustration opposite which shows a typical plant employing jigs 250mm (10 in) wide by 450 mm (18 in) deep.

The ability of the Digit to handle components individually (each on a separate work arm) makes it particularly suitable for use on automated transfer type production lines and the application of robotics.

A further production advantage with the Digit is that by processing components as they pass down the production line, the need to provide interstate storage of batches of work awaiting processing is avoided.

Straight-through Type Automatic Plant

In this type of plant, a number of lifting carriages are used at the transfer points between tanks to raise and lower the work. Traverse in the raised posi­tion is achieved by means of pusher rods whilst traverse in the lowered posi­tion is achieved by means of continuously moving conveyor chain.

Straight-through type plants are used for specialized large output requirements.

The Glydo System

Simple hoist systems have been in use for many years for handling work which was too heavy for manual processing but the hoists were difficult to control and the need to accurately locate the work load in a succession of tanks made it a tedious operation. From this basic system, the transporter type of plant was developed where the lift and traverse movements were provided by transporters running on tracks mounted on either side of the tank line. Plants of this type are known as the Glydo system.

The subsequent development of programme control units made it prac­tical to control and automate the movement of these transporters in a pre­determined pattern. This type of equipment is far more versatile than auto­matic plant previously available, it can be applied economically to situations where the work load is insufficient to justify conventional automatic equip­ment and in addition it can be employed for the handling of plating barrels and other heavy loads.

Development of cross transfer units permitted the introduction of multi­-line plants thus enabling the equipment to be arranged most effectively in the space available and also in relation to the work flow pattern of the factory. There are now in use plant having a variety of tank line arrangements, multiple lines with two or three tank lines linked by cross transfer system; in-line plants with the load and unload at the same end and the main plating tanks, e.g. nickel at the far end of the line, thus reducing traverse distances to a minimum and at the same time providing for the possibility of simple expansion of the line should it be necessary to add an additional plating stage. A modification of the cross transfer unit is the side loader, which enables work carriers to be brought out of the tank line in order to permit access to either side of the work load when loading and unloading the jigs or barrels.

Since Glydo plants were originally introduced into the plating industry, there have been a variety of transporter designs employed. The simplest arrangement is to have the tracks mounted along the tank line and supported by brackets attached to the tanks themselves. Raising the track level so that it is above the tank line has an advantage in that/the centre of mass of the transporter load particularly on barrel lines is at the track level and this greatly improves the stability of the system and also enables high transfer speeds to be employed. The mounting of the transporters from an overhead rail system has the advantage that complete accessibility to the tanks can be provided and in addition this arrangement can be employed where extremely wide tanks are in use. A further possibility is mounting the track alongside the tank line with a cantilever type of transporter. This provides accessibility to the tank on one side but is limited to barrel lines and to fairly narrow rack lines.

The range of equipment available extends from small light weight systems for processing, for example, printed circuit boards, to large heavy duty installations with transporters capable of handling loads in excess of 2000 kg.

The provision of process variation is an advantage in that it enables a number of differing finishes to be produced from one plant and also permits changes in specification to be made without heavy expense on plant alteration. The provision of the facility for programme variation may, however, result in a reduction in the overall efficiency of the plant, in that there will be occasions when the equipment is not fully utilized.

To meet differing process and production requirements, a number of variants on the Glydo system have been developed

These include:

Model 2 Glydo with transporters on raised tracks.

Model 3 Glydo with cantilever type transporters.

Model 5 Glydo with transporters on tank mounted tracks.

Glydair with transporters carried from an overhead runway.

Glydette with transporters on tracks just above tank level.

Model 2 Glydo

In the Model 2 Glydo, the positioning of the transporter tracks at eye level provides a number of distinct advantages: the traverse system is in line with the centre of gravity of the load, it provides a more stable system, and as a consequence permits the use of higher traverse speeds than are permissible with either tank mounted or overhead rail type systems.

The process tanks are more readily accessible for solution preparation and maintenance, and they can also be easily removed should they need to be replaced without affecting the track structure. Tank widths upto 10 metres (33 ft) can be accommodated.

Model 3 Glydo

In the Model 3 Glydo, the transporters are of a cantilever design and carried from tracks mounted on a framework along the rear of the tank line. This design permits complete accessibility to the working side of the plant, and is employed for specialized applications, as for example, the etching of turbine blades in the aerospace industry.

Model 5 Glydo

In the Model 5 Glydo a tank mounted track assembly is employed to provide a simple—low capital cost—electroplating line. The transporters may be controlled manually, or automatically by means of a programmed controller incorporating a photoelectric cell type reader.

The Model 5 Glydo design meets the need in certain areas and developing countries for equipment at an intermediate technology level.

Glydair

In the Glydair design, the transporters are mounted from an overhead track, which may be supported from the building structure, or carried from a free-standing framework. The use of the Glydair design permits free access to the process tanks and in addition the system can be applied to very wide tanks.

Glydette

The Glydette was originally introduced as a low cost, versatile transfer system, which employed a hand propelled transporter having a powered lift thus removing the effort but retaining the simplicity and versatility of manual operation. The special mounts for transporters enable them to be moved at the touch of a hand and a simple and positive station location is provided to ensure that the transporter is correctly positioned for the lifting and lowering operations.

The Model C Glydette is a development on the original design. As with the Model A, the tracks on which the transporters operate are mounted just above the tank line, but instead of being carried from the tanks themselves they are mounted on a coated steel frame work which also supports the process tanks. The tank/track support frames are of a modular design and each unit normally holds three tanks. The plant is made up by linking together the necessary number of frame units and to permit alignment on site, jacking points are provided. In addition, to simplify plant installation, electrical, water and drainage services may, if required, be prefabricated in the frame units. The Glydettes incorporate many important features such as completely enclosed track wheels, safety guards and smooth speed change and braking, preventing undue work swing and workload shock; these all reduce maintenance and add to operator safety.

The modular design Model C Glydette is particularly suitable for the plating of printed circuit boards.

Special Transporter Designs

Combined Barrel and Ruck Transporters

Transporter type equipment is now in use for handling work mounted on racks, or enclosed in barrels or baskets. By the use of barrels in tandem it is possible to arrange for both rack and barrel work to be carried through the same process line without the need to modify the anode arrangements when changing from rack to barrel processing.

Transporters with Integral Drip Tray

In mechanized plating plants, it is usual for a water rinse to follow each treatment stage to avoid the danger that cross contamination might occur if unrinsed loads were taken over other process tanks. One possibility for reducing the number of these tanks is to have rinses between alternate process tanks and where necessary to move back down the line to the rinse rather than continue in a forward direction. Another approach is to fit the drip tray to the transporter so that any solution dripping from the load is collected in the tray rather than allowed to fall into another tank. While such an arrangement permits a reduction in the number of rinse tanks and hence the total length of the process line there are limitations to the practical reduction in view of the need to separate certain of the rinses and also to provide sufficient rinsing on the line to handle the total work flow.

Dual Lift Transporters

To reduce the number of traverse movements, which the transporter has to undertake, a transporter with two independently operated hoists may be used. In operation, the transporter would, for example, pick up a load with the rear hoist, move to the required station, lift out the work with the front hoist and then move forward to deposit the load on the rear hoist into the now vacant tank. Thus, the two steps of unloading a tank and putting in a new load may be undertaken with a single transporter movement rather than with the two movements, which are required with the standard transporter.

Methods of Transporter Control

Glydo transporters may be controlled automatically by means of a programmed controller as described on the next page, alternatively, the plant may be controlled manually by means of a simple control panel on the side of each transporter. Where a very simple transfer system is required, then the push-along Glydette may be considered. With this unit, a power lift is provided but the transporters are traversed manually from tank to tank.

Manual control can be at the individual transporters themselves or at a central control desk. On each transporter a ‘joy-stick’ type control lever is provided and the stick moved in the direction of movement required, inter­locking being provided to prevent mal-operation of the units. For example the ‘joy-stick’ may be pulled forward and then moved to the right to initiate a vertical lift followed by a right-hand horizontal traverse. At the conclusion of the lifting operation, the transporter automatically moves to the right until the ‘joy-stick’ is moved to the neutral position. The transporter then travels on until it reaches the next process station and stops in the correct position for the next movement.

Programmed Controllers

With automatic transporter type processing plant, e.g. the Glydo range, a programmed controller is employed which issues instructions to the transporter or transporters to lift, lower, traverse left or right, in order that the work loads may be taken through the required treatment sequence. The programmed controller may also control the operation of ancillary equipment such as rectifiers, cross transfer units, centrifugal dryers, and monitor the process solutions so that they may be kept at the optimum operating parameters.

Programme Preparation

Before any instruction can be issued to the programmer, it is necessary to prepare a list of the movements required and normally this is in the form of a time/movement graph. To prepare this type of information it is necessary to know:

       (a)        The process tanks in order of use.

       (b)        The physical order in which the tanks are arranged. This will vary dependent on whether the plant is loaded and unloaded the same end or opposite ends.

       (c) The immersion times for each process together with an indication as to the degree of variation in time which is acceptable.

       (d) The output required.

From the time-movement graph prepared on the basis of this information it is possible to establish:

       1.  The number of transporters required.

       2.  The ‘beat’ or area over which each transporter needs to operate.

       3.  The number of barrels or flight bars, (work carriers required).

       4.  The precise immersion time for each process.

       5.  The times to lift, traverse left or right and where to stop.

This information is then converted into a form in which it may be read by a programmer as it moves through the processing sequence.

 

Fig. 1. Typical Transport Time/Distance Graph.

In the graph, the solid line shows movements of the transporters whilst carrying work loads, the broken lines show movement of the transporters when unloaded, and the breaks in the lines indicate periods when the Glydo transporters are awaiting instructions.

Programming Systems

Developments in programmers has paralled that of communications systems; starting with electromechanical relays and unit-selectors; moving to solid state switching and the use of integrated circuits in the controller, and most recently micro-processor/computer control.

The choice of system will be influenced by the number of activities and parameters, which need to be monitored and controlled; the information, which must be provided, and the level of technology, which is appropriate to the plant and its situation.

Today a control system based upon a microprocessor with the peripheral equipment, and suitably programmed, would be the first choice. Electromechanical systems with, for example, a photoelectric reader taking instructions stored upon a perforated tape or sleeve, may however be used where an advanced electronic device would not be appropriate.

Photoelectric Cell Type Reader

The programmed controller in which the programme of transporter movements is recorded as holes in a plastic tape which is read by a photo-­electric cell system is typical of the equipment employed prior to the introduction of the microprocessor. The perforated tape or sleeve is traversed between a light source and a series of photoelectric cells. Where the sleeve is perforated, electrical impulses are generated and these are employed to control the operation of the transporters initiating the required lift and traverse movements.

The reader incorporates a number of tracks which collectively control the lift/lower; traverse left and right movements of the transporter; the stop positions at the various process tanks, and the monitoring system to check the operation of the transporter to ensure that each movement instructions has been correctly carried out. Where more than one reader is used, all the tapes or sleeves are synchronized at the start of each cycle.

For stages where the immersion time exceeds the single cycle time, e.g. at the electroplating stages, multi-station tanks are provided. The programmed controller directs the transporter to the multi-station tank and an additional relay system selects the particular station into which the work is to be lowered.

To change the programme, it is merely necessary to insert a fresh tape or sleeve into each reader, the points at which a programme change can be made being indicated by the illumination of the ‘programme change’ pilot light on the panel. It is generally necessary to ‘run out’ one batch of work before changing the programme.

Microprocessor and Computer Control

The term programmable electronic system (PES) is perhaps the most descriptive of the types of microprocessor (microcomputer) control which are now being employed with transporter type processing plant. These controllers differ from previous generations of conventional relay and electronic systems in that they do not have to be built individually to the specific requirements of each process line but can be interfaced with a wide range of plant and process sequences.

Microprocessor based systems provide extremely reliable performance and their very large capacity for the storage and handling of information makes it practical to extend control to a wide range of process parameters, and also to provide management and production information.

The most important single advantage of microprocessor control is the flexibility, which the system provides. The same hardware (electronic equipment) can be employed for a variety of plant/process control require­ments or information handling, with only a modification to the software.

Control of the transporter movements

The logic system checks the positions of the transporters, and also where required the individual work carriers, from information provided by proximity switches mounted on the transporters themselves also at appropriate positions along the transporter tracks. This information is compared with that given in the programme stored in the memory and the appropriate instructions are issued to the transporters to undertake the necessary hoist/traverse operations.

A mimic LED display may be incorporated to indicate the transporter and flight bar positions and can also indicate the positions required for plant start up or change in programme. A number of alternative programmes can be stored in the memory to be called up when required, and fail-safe facilities incorporated to prevent start-up or change in programme, should any of the transporters or work carriers be out of position.

In addition to fully automatic control, the transporters may also be controlled manually via a joystick or pendant switch with the controller monitoring the movements so that when the plant is returned to automatic operation, the normal processing cycle can be continued. There is also provision for emergency manual control with the programmed controller inoperative.

Additional Plant operation Functions

The controller may also be employed to initiate and monitor the operation of cross transfer units, automatic work loading and unloading equipment, and also dryers, so that these are synchronized with the operation of the transporters on the plant line,

Process Control

The large capacity of the new types of controller permit the incorporation of a number of facilities which enable the various treatment processes them­selves to be monitored, controlled and adjusted so that they operate under optimum conditions, for example:

The temperatures of the various solutions on the process line may be monitored using contact type thermometers, or alternatively thermocouples or resistance thermometers in order that the actual temperatures may be recorded. Proportional integral differential loop control may be incorporated and used in conjunction with modulating control on the heating or cooling system in order to give very fine temperature control.

Automatic control of rectifiers may be provided in order to reduce the voltage before unloading, followed by adjustment to a specified value when the tank is reloaded. In addition, constant current, constant voltage, constant current density control can be incorporated. For example, the controller can accept an analogue signal from a shunt, which is proportional to the current flow, compare this with a reference level, and initiate an adjustment of the rectifier output so that the correct current is applied to the load. The reference level is computed from information fed in via switches or a keyboard when the work is loaded on to the plant. It may represent, the required plating current; voltage; ampere hours required per load; current density or work area.

Solution levels may be monitored and appropriate instructions issued to circulating pumps and control valves to make the necessary adjustments.

Chemical additions may be made automatically by the control of dosing pumps or control valves on the basis of process usage or change in composition. For example, electroplating additives may be added on an ampere hour basis, and acid/alkali for control of solution acidity on the basis of regular pH determinations.

Fault Indication

With microprocessor control, facilities are provided to simplify fault location. Error checking facilities are built into the programming and an alphanumeric display can be incorporated in the control panel to indicate the type and location of faults which might develop or any error in plant operation.

Performance and Production data preparation and handling

The controller may incorporate facilities for the numerical display of solution temperatures, operating currents and voltages, power and water consumption and also store this information for subsequent processing on a mainframe computer. Information on each load of work processed can be tabulated, presented to the plant controller by way of a visual display unit or printer and stored for subsequent processing.

Entering the Programme

The programme or series of programmes may be entered into the memory of the programmed controller in a number of ways:

The programmes may be contained within a replaceable memory chip prepared by the plant supplier. In the event of a major change in programme requirements a new chip would be plugged in.

it may be keyed in directly, step by step, using a teletype or a keyboard. To simplify this operation, a translator may be incorporated in the controller to enable the instructions to be entered in plain language or by the use of specially designated keys.

it may be prepared as a perforated tape or magnetic tape which is fed into a reader attached to the equipment.

Where the plant incorporates process or sequence selection on individual loads, an additional keyboard or set of switches is provided in order that the necessary information can be keyed in for each batch of work.

Random Selection Control

With the development of microprocessor control, it is no longer possible to classify systems as Mixed programme’ or ‘random selection’, as a whole range of facilities can he incorporated by the use of appropriate software (programmes).

An example of the facilities which microprocessor control can provide is given by the plant for the hard chromium plating of piston rings illustrated on this page. The plant enables the plating requirements for each mandrel to be selected.

The microprocessor provides pre-set control of the transporter movements and of the ancillary equipment and in addition, a random selection facility which directs the hard chromium plating operation. Information on over 100 batches of work or mandrels can be stored in the memory to enable individual thickness requirements to be met. Each plating station takes two mandrels each of which is provided with independent rectifier control. Plating times can vary from 3 to 15 hours depending upon the individual thickness requirements. The current and voltage out-puts from each of the 32 rectifiers on the plant is sequentially monitored, and where necessary adjusted to the preselected values. The system ‘knows’ which is the next plating cell to be unloaded and arranges for the current to be switched off before the load is lifted out by the transporter. At the unload station, full details on each mandrel are recorded and automatically printed on to the work ticket.

Semi-Automatic Plating Plant

The term semi-automatic may be applied to process lines, which are manually controlled but employ mechanized systems of work transfer. This arrangement enables heavier workloads to be processed, as their weight and size are no longer limited to that which can be conveniently lifted by hand. At the same time, much of the versatility of manual processing is retained.

For work transfer, overhead hoists are often employed, particularly for large components, with either a single or twin track system depending upon the width of the process tanks. Equipment of this type is widely used for the processing of large components such as in the aircraft industry, and for the anodizing of aluminium extrusions. Hoist type plant is, in many instances being replaced by transporter type equipment e.g. manually controlled Glydo and Glydette, in view of the greater ease of control and the positive station location, which these systems provide.

Barrel Planting Plant

Barrel plating is widely employed for the bulk processing of small to medium sized components. Recent improvements in plant and processes have greatly increased the range of components which can be electroplated in barrels and now permit the application of heavier deposits, thus enabling specification finishes to be produced.

Barrel plating equipment can consist of multi-station units in which the plating, pre-and post-plating sections are combined in one plant, or single station units where the plating barrel is fed from an independent and usually manually operated cleaning line.

Suitability of Articles for Barrel Plating

The selection of articles for barrel plating is limited by their size, shape and weight. Massive or sharp cornered parts are liable to damage one another during the process and also result in abrasion of the barrel itself.

Flat articles, especially thin discs, washers, and light gauge sheet metal parts, tend to stick together when wet through surface tension of the solution, and some small pressings are apt ‘nest’ one inside another.

Barrel Types

Barrel plating units may be divided into two main types:

Perforated barrels, which are immersed in the plating solution.

Open-ended solid barrels in which the solution, the anode and the work are contained inside the barrel.

The choice of barrel is dependent upon the shape, size, density and the quantity of articles to be plated. For large outputs, particularly where specification thickness requirements have to be met, it is now usual to employ immersed barrels. Very small parts, however, such as fine screws and rivets may be plated in an open-ended barrel, e.g. a Typhon.

The particular plating solution to be employed can also collect the choice of plating barrel, and further information on this is given under the appropriate process headings.

The barrel plant may be arranged as a production line with mechanical transfer of the barrels from one stage to the next, e.g. the Glydette, or may consist of single station plating units, e.g. Electrominik barrel. With barrels such as the Electrominik, the articles to be plated are cleaned on a separate line and then transferred to the barrel for the plating process.

Immersed barrels range in sizes from 1070 by 400 mm (42 by 16 in) for large scale production down to small 180 by 100 mm (7 in by 4 in) diameter barrels for experimental and small applications. A number of different methods of transfer are available for immersed barrels. On multi-station plant, the Glydette, an overhead hoist, may be used, and for single station barrels, equipment such as Electrominik is employed.

The open ended type barrel is still used for small outputs, and it has the advantages of low initial cost, and the use of a relatively small volume of solution. It is suitable for processing a wide range of components, including those too small to be treated in small perforated barrels; it has, however, a lower efficiency than the immersed type of barrel, and the present trend is for this type of equipment to be replaced by immersed barrel plating units.

Immersed Perforated Plating Barrels

For the majority of applications horizontal barrels are employed but for certain high output requirements, oblique perforated barrels are employed. These have the advantage that they can be more easily provided with automatic loading and unloading facilities as part of a fully automatic process line.

Glydo/Glydette Barrel Plating Equipment

The articles to be plated are loaded into the barrels, which are then taken through the various pre-plating, electroplating and post-plating processes by means of a transporter system.

The Glydo plant is built up as a series, of process tanks, with the trans­porters mounted on tracks alongside the tanks. A Glydo plant may consist of only two or three tanks for a simple loading, plating, rinsing and unloading sequence, whilst large installations may be of thirty or more tanks involving differing cleaning sequences and a number of plating stations. The unit method of construction permits modification or extension of the plant to meet changing production requirements.

Horizontal Barrels

The size of the barrels employed is dependent upon the output required. Where small batches of work are to be processed, a compartmented barrel can be employed. The barrel container has a vertical partition providing two separate sections, each with its own cathode contact. Alternatively, a twin barrel unit can be used consisting of two barrels mounted on a single carrier with single or separate double motor drive. Barrels may be cylindrical with internal work breaks, or hexagonal using single sheet wrap-around con­struction.

Constructional Materials

The majority of plating barrels are now made in polypropylene and are suitable for continuous operation at solution temperatures upto 75° C (167° F).

Barrels fabricated in the G 76 type of polypropylene can be supplied with special interior surface finishes which prevent the articles from sticking to the barrel walls; protect the perforations against damage and can give an improve­ment in the throwing power of the plating process. For barrels, which have small perforations (e.g. 3 mm) the dimpled waffle type material is used whilst for barrels having perforations (upto 6 mm), the Polydome surfaced poly­propylene is preferred.

'C’ Series Barrels

The ‘C” Series range of barrels is a development of the conventional hori­zontal transportable cylinder units which have been used on hoist and trans­porter type barrel plating plants for a number of years. Developed initially for use on the Model C Glydette, the ‘C’ Series range of barrel units, incorporate a patented design of cathode connection, which eliminates the need for the traditional brass cathode horn and saddles. The 50 volt 3 phase pick-up blocks for the barrel drive supply, the mild steel guides for barrel location and all other fittings are mounted directly on the framework, which supports the tank and transporter.

The barrels are constructed from a new type of material, G76 polypropol-ene, and also feature patented self-sealing bearings which prevent the ingress of swarf and small work, thus extending bearing life.

Barrel Perforations

The standard perforation is a series of cylindrical holes. Where the holes are small (i.e. below 3 mm, in) the holes are counter bored from the outside to increase solution circulation and reduce the internal electrical resistance. For plating of small diameter articles such as pins, which would pass through the normal perforations, a herringbone or mesh type barrel may be used.

The ‘herringbone’ barrel is used for the plating of pins and similar articles. As indicated in the diagram, the perforations in the plastic walls of the barrel are drilled at an angle in a herringbone formation so that even small pins cannot pass through. At the same time, the holes are sufficiently large to ensure good solution circulation.

Herringbone barrels are available in Cub Major, Electrominik, Glydette and Glydo sizes.

The Electromesh barrel is employed for small work, particularly where precious metals are to be deposited on precision watch, instrument and electronics components. The fine 0.8 or 0.4 mm perforations enable very small components to be processed including those with delicate wire leads.

Cathode Contacts

The normal form of cathode contact consists of a length of heavy insulated flexible cable terminated with a steel cathode knob. (This is often known as a dangler contact.) Two contacts are provided entering through the stationary bearings at either end of the container. For certain types of work, a shaft may be fitted to the barrel to carry the cathode contacts or, alter­natively, other contacts may be provided.

Current Control

Where the barrel is operated off an individual rectifier, off-load or on-load voltage control can be provided, depending upon the situation. Where a number of barrels for the same plating process are operated off a single low voltage supply, then it is advisable to provide individual off/on control.

Voltage

The voltage necessary for barrel plating is dependent upon the type of barrel and the electrolyte used, but in all cases is somewhat higher than that required for still vat plating with a similar type of solution.

With a self-contained open-ended barrel using a highly conductive electro­lyte, such as acid tin solution, the internal resistance is small, hence, a pressure of 3 volts may be sufficient. Generally speaking, however, a minimum of 6, and an average of between 8 and 16 volts, is necessary for barrel deposition, and in some cases as much as 20 volts may be required.

Speed of Barrels

The correct speed of rotation is governed by the diameter of the barrel and the nature of the articles that are to be plated. Small barrels are usually driven at 10 to 15 revolutions per minute, and large at 6 to 12 revolutions per minute, but a reduction of speed below these limits may be necessary in special cases.

For bright zinc and bright cadmium plating, it is advisable to use a speed of 5 to 6 r.p.m., even with barrels of medium size whilst for phosphating the usual speed is ½ r.p.m.

Anodes

In view of the fact that a barrel load of small articles usually presents a very big surface area, it is desirable to provide as large an anode surface as possible, in order to maintain the metal content and general balance of the solution.

With the self-contained, open-ended type of barrel, all that is necessary is for the operator to replace the anode whenever it becomes thin and much reduced in diameter. In some instances, these anodes are cast with a heavily ridged or corrugated face, so as to increase the effective surface area for a given diameter.

With the other types of barrel, namely those in which the solution is con­tained in a tank, the anodes must be examined regularly and new ones intro­duced from time to time to maintain the necessary surface area.

To prevent corrosion and poor electrical contact, the rods on which the anodes hang should be protected against splashing by the solution. The anode hooks must be of the same metal as the anodes or one that does not dissolve in the solution, and should be long enough to permit suspension of the anodes at the proper depth.

 

Electroplating Equipment

Process Tanks

For electroplating and allied processes, chemically resistant containers are generally necessary for the solutions employed.

Welded Steel Tanks

Welded steel tanks, suitably lined if required, are used for the majority of electroplating processes, but other types of container may be used when operating conditions permit. The steel tank in its usual form consists of an open rectangular box with welded joints and an angle stiffener on the top edge, For cleaning and rinse tanks the outlet can be filted to the bottom of the tank. For plating tanks it is usual to fit the outlets to the end of the tank

Steel tanks are also available provided with a sloping bottom. This form of construction greatly simplifies emptying and cleaning out. The extra cost of this type of tank is more than justified by the simplification of plant and process maintenance, which it permits.

Unlined steel tanks, preferably double welded, are employed as containers for alkaline cleaning and plating solutions, also cyanide dips and sulphide bronzing baths.

Plastic Tanks

Plastics tanks have a wide range of application in electroplating and other solution treatments in view of their inherent resistance to corrosion and chemical attack, light weight as compared with metal, and good electrical insulation properties.

A number of differing types of tank construction are available including

Polypropylene welded tanks

Polythene moulded tanks

Glass fibre (GRP) tanks

PVC and polypropylene GRP reinforced tanks.

The choice will depend upon the specific application, and in particular - the solution to be contained, the operating temperature, the tank size and situation.

Polypropylene welded tanks are constructed from sheet material and provided with reinforcement bands to prevent distortion of the tank when full of solution. They are suitable for the majority of solutions used in electro­plating and can be operated at temperatures up to 70° C.

Tanks moulded in rigid high density polythene are available in a wide range of sizes upto about 1250 litres (275 gal) capacity. They are suitable for the majority of solutions used in electroplating and pickling, and when made from the rigid grade of polythene are effective for use upto the boiling point of water with suitable tank support.

Plastic Tanks Reinforced with Glass Fibre

These tanks are fabricated in rigid PVC or polypropylene and then covered on the outside with a glass fibre plastic laminate (GRP) in order to provide the required mechanical strength. The standard range of tanks has capacities from 102 litres (22 gallons) upto 1860 litres (410 gallons) and they are suitable for the majority of plating and pre-treatment solutions. The PVC is suitable for use upto about 70° C (160° F) and the polypropy­lene upto boiling point 100° C (212° F).

Glass Fibre (GRP) Tanks

Tanks of polyester GRP construction are now used extensively for rinses and dilute acid dips. It is not advisable to use the tanks for any plating solutions except cool working, mildly acidic or neutral solutions which are not sensitive to the organic compounds which may be leached from the tank.

The tanks should not be used to contain strong acids, alkalis or cyanide solutions. At elevated temperatures, even dilute solutions can attack the resins used and it is particularly important therefore to mix substances like sulphuric acid, which heat up on dilution, in a separate metal or plastic lined vessel and then transfer to the fibreglass tank when cool.

The chemical resistance of GRP tanks depends upon the type of resin employed in the moulding and on the way in which it is layed up and cured.

Stainless Steel

Stainless steel (18 per cent nickel and 8 per cent chromium) containers can be used for nitric acid and other oxidizing acids, e.g. chromic acid/ sulphuric acid pickling solutions.

Stainless steel is not suitable for use in hydrochloric or sulphuric acid solutions or for alkaline solutions where the stainless steel may become anodic or bipolar.

Stainless steels of widely differing compositions are available. It is therefore important when ordering stainless steel tanks that the process and operating temperature be specified.

Tank Lining Materials

Rubber

Rubber is the most widely used material for tank lining. For this purpose, it is available in two main grades soft and hard.

Whilst the soft grade of rubber can be specified for water rinse tanks and for hydrochloric acid containers, it is more usual to supply the same hard grade for all tanks, in order to simplify plant layout and modification.

The hard grade is used for electroplating solutions. For this purpose it is essential that a suitable quality of rubber be employed which is free from any constituents such as fillers or accelerators, which may have a detrimental effect on the plating solution.

The rubber quality is of particular importance with bright nickel and acid copper plating solutions; for these, an approved grade of high temperature cured rubber, e.g. Vulcron, should be specified.

With rubber-lined tanks, a maximum operating temperature of 70° C (160° F) is advised.

For bright nickel and also acid copper plating solutions, it is recommended that the linings be pre-treated with hot dilute acid as described below.

Tanks for cyanide plating solutions should be pre-treated with hot caustic soda solution as described on the next page.

Natural rubber is not suitable for use with strong oxidizing solutions, such as nitric acid and chromic acid.

Treatment of Rubber Linings

For Bright Nickel and other Acid Plating Solutions

Before use, new rubber-lined tanks and equipment should be treated with hot dilute acid for a period of at least 8 hours. Where stainless steel com­ponents are included in the pumps or filtration system, dilute sulphuric acid is employed. Where the system is entirely of rubber or plastic, dilute hydro­chloric acid may be used.

Using sulphuric acid, the plating tank is filled to about three quarters of its capacity with clean cold water, the sulphuric acid is then added slowly and carefully with stirring, care being taken to ensure that the concentrated acid does not come into direct contact with the rubber.

Sufficient acid should be added to raise the concentration of solution to 10 ml/1 (1½ ft oz/gal). When the necessary quantity of sulphuric acid has been added and the solution thoroughly mixed, the temperature is raised to 60° C (140° F) and maintained at this value for at least 8 hours. To treat any associated rubber-lined equipment, e.g. filter units and pumps, the acid should also be circulated through these. It is important that the cloths be removed from the filtration unit prior to this treatment, otherwise the fabric may be damaged. After treatment with dilute acid, the tanks should be washed out with water before use.

Where there are no metallic parts in contact with the solution and the equipment is wholly of rubber or plastic, hydrochloric acid solution having a concentration of 50 ml/1 (8 fl oz/gal) may be used in place of the sulphuric acid described above.

Acid Cleaning of Rubber Lined Tanks fitted with Titanium Coils

Where titanium steam coils are used, anodic protection of the titanium is necessary during the sulphuric acid cleaning period. A temporary graphite or lead plate having a minimum surface area of 80 cm2 (12 in2) should be hung from the cathode rod and a 3 to 4 volt DC supply connected between the cathode rod and the titanium coil, the coil being connected to the positive. The plating rectifier may be used for the DC supply or alternatively two cells from a car battery can be employed. The current required is quite small and rapidly falls to a few hundred milliamps. A 1 ohm (5 ampere rating) resistance should, however, be included in the circuit to afford protection against accidental short circuit and to restrict the current surge.

An alternative method which, can be adopted is to carry out the acid cleaning process before the titanium coils are fitted and to arrange for the dilute sulphuric acid to be heated by independent means. One method sometimes used is to heat the solution by injecting live steam directly into it. Where this method is employed it is essential that suitable steam injectors be used and that a pressure reducing valve be fitted. Care must be taken to avoid damage to the rubber lining by direct impingement of the steam on to the rubber.

For Cyanide Plating Solutions

With cyanide plating solutions, it is advisable to pre-treat new rubber linings with a hot caustic soda solution. The solution is retained in the tank for at least eight hours and where possible the temperature maintained at 50 to 70° C (120-160° F). After treatment the tank should be well washed out with water, the rubber lining then slightly scoured with a fibre or bristle brush and again washed out before being put into use.

A suitable concentration for the caustic soda (sodium hydroxide) is 100 g/1 (16 oz/gal) or 25 to 40 g/1 (4 to 6 oz/gal) where the solution can be heated. The material should be carefully dissolved, with stirring, in cold water in a separate steel tank and then transferred while still hot to the plating tank, (sodium hydroxide evolves heat upon dissolution.)

Key to Table

R—Recommended     S—Suitable

1.     With, preferably, a loose inner lining of rigid plastic sheets or reinforced glass sheets.

2.     Antimonial lead alloy with a loose inner lining of rigid plastic sheets or reinforced glass sheets. When starting up new chrome plating tanks or re-commissioning re-lined tanks, it is important that the temperature of the chrom­ium plating solution be brought up as rapidly as possible to 60 to 65° C (140 to 150° F). In this way a protective film is formed on the surface of the lead. Under no circumstances should cold chrome solution be left in contact with alloy lead, until the above treatment has been applied.

3.     Vulcron, pre-treated with hot dilute acid.

4.     Vulcron, pre-treated with hot dilute alkali.

5.     Stainless steels of widely differing compositions are available. It is, there­fore, important when ordering stainless steel tanks that the process and operating temperature be specified.

6.     When preparing dilute sulphuric acid or dissolving up caustic alkalis, in plastics or plastics lined tanks, care must be taken to ensure that the solution temperature does not rise above 70° C (160° F) or with polypropy­lene 100° C (112° F). These substances evolve heat on dilution with water and can produce local areas of heat well in excess of 100° C (212° F).

7.     In the case of sulphuric acid, the concentrated acid should be added slowly and carefully to cold water whilst the solution is continuously mixed. If there is an excessive rise in temperature, then the acid additions should be suspended until the solution has had time to cool.

8.     With potassium and sodium hydroxide and other caustic mixtures, the alkali should be added slowly to cold water with thorough mixing. Great care must be taken to avoid the accumulation of any quantity of solid alkali on the bottom of the tank.

7.     A band of rigid PVC should be bonded to the Ilex at the solution/air interface and should extend 152 mm (6 in) above and below the optimum solution level.

8.     With a sprayed PTFE lining or a loose plastic liner.

Polyvinyl Chloride

Polyvinyl chloride (PVC) is resistant to almost all solutions employed in electroplating, provided the operating temperature is below 70 C° (160° F.)

For chromium plating and other solutions, tanks lined with a special grade of soft plasticised PVC may be used. This coating is supplied under the name Ilex.

For other linings and exhaust ducts, a laminated material is used consisting of layers of rigid and plasticised PVC firmly bonded together. The rigid PVC surface is in contact with the solution or fumes, and the softer plastic­ised PVC provides a surface, which can be bonded to the tank and also prevents cracking developing in the rigid PVC layer.

The table gives general recommendations and reference should be made to the appropriate process section for more detailed information upon plant requirements.

Ilex Grade Plastic Lined Tanks

These tanks are lined in a special grade of soft plasticised PVC, which has a number of advantages over rigid type PVC linings. The flexibility of the coating enables it to accommodate differences in thermal expansion between the plastic and the steel and absorb any stresses, which may be produced. The high flexibility of the coating also permits it to be applied to complex structures and greatly simplifies the internal lining of tanks and other containers. The coating is firmly bonded to the steel and can be used at temperatures upto 70° C (160° F).

By careful selection of the plasticisers in the PVC film, a very high chemical resistance is obtained, this being only slightly less than that provided by rigid PVC. The coatings do not age rapidly, neither are they susceptible to degradation by oxidizing agents.

These PVC lined tanks are suitable for all types of plating solution, including bright and hard chromium, acid dips and pickling solutions, alkaline solutions, and for the storage of a wide range of chemicals.

Nitric acid based solutions are the exception however and a rigid PVC lining is recommended rather than Ilex, which should not be used. On steel tanks a laminate is used consisting of layers of rigid and plasticised PVC. The rigid surface is in contact with the nitric acid and the plasticised PVC provides a resilient surface, which can be bonded to the tank.

Lead

Chemical lead is used for the lining of tanks for sulphuric acid, dull nickel and acid copper plating solutions. For chromium plating solutions, and also where a higher mechanical strength is required, antimonial lead alloy is employed. Lead-lined chromium plating tanks should be pre-treated before use.

Lead must not be used for holding nitric acid, or any alkaline cleaning or plating solution (other than silver and certain copper solutions). It is attacked by hot hydrochloric acid, and is not recommended for cold hydro­chloric acid or aqua fortis.

Materials of Construction—Containers, Hooks, Dipping

Baskets

Resistance to corrosion is influenced by many factors, such as the tempera­ture and concentration of the liquid, and in the case of metals those which may be affected by galvanic action and the presence of impurities in the solution, some of which will accelerate and others inhibit attack. The recommendation as to the suitability of a material does not imply that it is entirely resistant and will withstand corrosive liquids indefinitely, but that it will give good service under normal conditions.

Aluminium

High purity aluminium hooks and dipping baskets are suitable for use in strong nitric acid and in aqua fortis bright dips. Wire and jigs are used for the suspension of aluminium articles undergoing anodic oxidation, and aluminium tanks are satisfactory containers for nitric acid at high con­centrations.

Aluminium must not be employed in caustic or strongly alkaline solutions, and is unsuitable for sulphuric, hydrochloric and hydrofluoric acids.

Glass

Chemical glassware and apparatus including measures, containers and pipe work are suitable for all solutions employed in electroplating and allied pro­cesses with the exception of those containing hydrofluoric acid or other acid fluorides. Fluoboric acid solutions are satisfactory in glass containers provid­ing excess boric acid is present in the solution. Where glass is used in contact with hot highly alkaline solutions, then there may be some surface attack, which could result in contamination of the solution.

Brass, Bronze and Copper

Copper wire is generally used for the suspension of small articles during plating, and brass strip and rod for the construction of jigs. Acid-resisting phosphor bronze hooks are suitable for handling heavy work in sulphuric or hydrochloric acid pickles, although not entirely resistant to the latter if hot. Brass and copper hooks may be similarly employed, and brass wire baskets for small articles. These metals are also used in alkaline cleaning solutions, but should not be made anodic in the circuit.

These metals will not withstand the action of nitric acid, aqua fortis and chromic acid dips. Brass is unsuitable for use in hot hydrochloric acid.

Monel Metal

This nickel alloy is highly resistant to sulphuric acid and is used for hooks and dipping baskets. It is also used for cold dilute hydrochloric acid, but is attacked by the hot acid according to the temperature and degree of concentration. Monel metal may be put through alkaline degreasing solutions.

Monel metal is unsuitable for use in aqua fortis and nitric acid.

Nichrome (‘Chrome’ Wire)

Nichrome hooks and wire baskets are suitable for use in nitric acid, aqua fortis and chromic acid dips. Nichrome is resistant to alkaline solutions but the metal must not be made anodic in an electrolytic cleaning bath.

Nichrome should not be used for hydrochloric acid.

Rods & Connections for Process Tanks

Electroplating tanks are fitted with suitable anode and cathode connections.

For the suspension of the anodes and articles in the plating solution, brass or copper tubes or solid rods are used; for heavy currents or for carrying greater loads of work, solid ‘D’ section or hollow ‘U’ section bars are employed.

Fixed bars are supported on porcelain, polyethylene or phenolic insulators which are either screwed to a wooden or plastic capping on top of the tank, or fastened directly to the tank lip. In automatics of the Glydo type where generally the heavy section rods are used, the fixed supports are of cast metal, which are fastened to the tanks or support framework. If these rods are carrying current they should be suitably insulated from the main structure. Because the work bar is movable in this type of equipment, the cathode con­tacts are of a specially designed ‘V’ shape to provide both a good contact and to guide the flight bar into position.

Round tubes or rods can be jointed together by means of the various rod connectors shown in the illustration or can have clip-ends when there is a need for regular adjustment. If tanks have more than one anode or cathode bar, the rods are extended just beyond the tank and cross connections fitted so that all bars of like polarity are joined together.

Solution Heating

For many of the processes associated with electroplating it is necessary to heat the solution. The available methods of heating include steam, hot water (medium or high pressure), liquid phase, gas and electricity.

The most satisfactory methods of heating are steam, hot water, and liquid phase, but where these services are not available and the size of the plating plant does not justify the installation of a boiler, then gas or electricity can be employed. The capacity of the boiler should be such that the solutions can be heated from cold to the operating temperature within the time required. This time is usually 3 to 4 hours.

Stem Heating

Fig. 1. Steam Heating.

Steam can be raised using any of the available means of heating, e.g. solid fuels, gas, oil and electricity. The steam pressure for heating can vary over a wide range; the extremes should, however, be avoided, and it is either advantageous or economic to generate super-heated steam for plating process heating. The usual pressure range is 1.5 to 4 bar (20 to 60) lb/in2. It should be noted that the higher the steam pressure, the greater the temperature difference that will exist between the steam and solution. This, in turn, reduces the size of the heating equipment required.

The efficient use of steam depends upon properly sized and maintained steam traps and control valves. The steam trap ensures that condensate is discharged with the minimum loss of ‘live’ steam. The correct type and size of control valve will permit the accurate regulation of the solution temperature.

Electrolytic process tanks must have steam coils provided with insulated flanges to prevent low voltage D.C. leakage currents between the tanks by way of the steam lines.

With steam heated tanks, it is now usual to return the condensate to the boiler hot well in order to conserve energy. It is however essential that con­ductivity or pH control is fitted to the return line to detect the presence of contamination as a result of a leak in a steam coil.

Four main methods are available for using steam for the heating of solutions:

Steam heating coils or plates submerged in the tank.

Heat exchangers external to the tank.

Water jackets surrounding tank.

Live steam injectors in the tank or jacket.

Steam Coils

Steam coils immersed in the solution are the most widely used method of heating. The coils should be made of, or clad with, a metal, which is chemically resistant to the solution in which they are to be immersed.

The following materials are used for steam heating coils:

Plain or galvanized steel,