Racking
Racks should have type 304 or 430 stainless steel or phosphor bronze tips and be coated with vinyl plastisol. Good plating practice requires good rack maintenance. Rack tips should be kept free of electroplated buildup and damaged plastisol should be repaired.
Cleaning
Usually soak cleaning and cathode cleaning in alkaline solution are required.
Activation
The solution is used to remove any residual chromate from the pickling acid and to produce an oxide free surface. A typical composition is:
Phosphoric acid, H3PO4, 85% 20% (v0l) 200 ml
Ammonium acid Flouride, NH4HF2 90 g/l
Temperature 16 – 30oC
Time 1 to 2 min
Zincate Solution
Zinc Sulfate, monhydrate, Zn SO4 . H2O 30 g/l
Tetrasodium pyrophosphate, Na4P2O7 120 g/l
Lithium Flouride, LiF, or 3,75 g/l
Sodium Flouride, NaF 5 g/l
Sodium Carbonate, Na2CO3 5 g/l
pH (electrometric) at 24oC 10.2 to 10.4
Temperature 60 – 76oC
Time 3 to 10 minute
Agitation, work movement or solution agitation
Equipment – type 316 stainless steel tank and heater or a rubber tank and Teflon heater.
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