ã€China Aluminum Network】 In order to ensure good adhesion of the plating layer, after the aluminum is immersed, the copper or nickel should be pre-plated in a solution that is near neutral or weakly alkaline to prevent the etching solution from being electroplated. Impregnate the plating.
Pre-plating copper can be performed in a conventional pyrophosphate solution. After flashing, it should be flash plated at high current density for 1 to 2 minutes.
Pre-plating copper can also be carried out in a cyanide solution. The process specifications are as follows:
Copper cyanide (CuCN) 42g/L
Total amount of sodium cyanide (NaCN) 50 ~ 55g/L
Sodium cyanide free (NaCN) 5.7g/L
Sodium potassium tartrate (KNaC4H4O6·4H2O) 60g/L
Sodium carbonate (Na2CO3) 30g/L
Temperature 40~55°C
pH 10.2 to 10.5
Charged into the groove under 2.6A/dm2 flash plating 2min, in the 1.3A/dm2 plating 3 ~ 5min. Pre-plating of nickel is carried out in a neutral solution. The process specifications are as follows:
Nickel sulfate (NiSO4·7H2O) 140g/L
Ammonium sulfate [(NH4)2SO4]35g/L
Nickel chloride (NiCl2·6H2O) 30g/L
Sodium citrate (Na3C6H5O7·2H2O) 140g/L
Sodium gluconate 30g/L
Temperature 50～65°C
pH 6.8 to 7.2
Current density 2A/dm2
5min
However, when galvanizing aluminum, brass, silver, or chromium, the plating may not be pre-plated, but the lower tank must be charged.