Current density 01 to 32 Adm2 1 to 30 Aft2 16 Adm2 15 Aft2 optimum

• Agitation: cathode rod, solution, or barrel. Still racks may be used at low current densities.

• Anodes: high-purity nickel in polypropylene bags

• Filtration: continuous through polypropylene or chlorinated polyvinyl chloride (CPVC) above 60 °C (140 °F)

Preparation. Metallic substrates should be cleaned. A common acid cleaning procedure is a 10 to 20% HCl bath immediately before plating. Steel substrates should be plated with an alkaline copper or acid nickel strike coating.

Equipment. All equipment in contact with the plating solution should be nonmetallic. Tanks and filters should be polypropylene or CPVC. Heaters should be fluorocarbon coated.

Handling Precautions. Gloves, protective clothing, and goggles should be worn when handling electrolyte solution or its components.

Environmental Considerations. Electrolyte solutions and their components should be treated according to procedures for fluoride- and cyanide-containing wastes. They should not be mixed with metal-bearing waste streams, because they contain metal chelators (Ref 10, 11).

Table 7 is a troubleshooting guide to tin-nickel plating solutions.

Table 7 Troubleshooting guide for tin-nickel plating solutions

Problem

Possible cause

Remedy

Powdery gray deposit

Current density too high

Use a lower current density.

Nickel content too low

Analyze nickel content, add nickel chloride if necessary.

Dull or black deposit

Tin content too low

Analyze tin content, add stannous chloride if necessary (starter concentrate must be added at the same time as stannous chloride).

Brittle or milky deposit

Low replenisher

Add replenisher.

Metallic contamination

Remove metal by electrolyzing solution.

Dark or black deposits in low-current-density plating areas

Copper contamination

Eliminate source of contamination, remove copper by electrolyzing.

Dark deposit with standard current density or burn with high current density

Organic contamination

Filter solution through activated carbon. Never add hydrogen peroxide, potassium permanganate, or other oxidizing agents.

Incorrect alloy composition

Incorrect solution composition

Analyze tin and nickel contents of bath and adjust.

Nickel content increases during operation

Excess anode area

Decrease anode area.

Source: Ref 10

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