Many aluminum materials used in military products require silver plating on aluminum parts in order to increase their electrical conductivity. The 786 plant in Xi’an City has undergone many tests and has eliminated the thickening and mercurying of copper plating in the old process. Improvements have been made to the pre-treatment process and good results have been achieved. The product qualification rate is above 98%.

1. The main process flow is after the organic solvent is deoiled, chemical degreasing → acid activation → leaching zincate (once) → dezincification → secondary zinc leaching → pre-plating copper → silver plating.

2. Main process recipe acid activation For normal aluminum parts can be activated directly in nitric acid; for silicon aluminum parts, the activation solution should be added with appropriate amount of HF; copper-aluminum parts should be carried out in H2SO4: HNO3 1:1 ratio acid activation.
Zinc leaching zincate is to replace a layer of fine plating on the aluminum parts to increase the bonding force. The process formula is as follows:
NaOH 500-550g / L
ZnO 100g / L
Sodium potassium tartrate 10-15g / L
FeCl3 2g / L
NaNO3 1g / L
Temperature 45-60°C
Time 20-40s
For general aluminum and alloy parts, the formula can be pre-plated with zinc after dipping zinc. For the copper-containing aluminum alloy, the previous zinc-impregnated layer should be removed with a 1:1 HNO3 solution, and then the following formula should be used for the second zinc dipping:
NaOH 100g / L
ZnO 20g / L
Potassium sodium tartrate 20g / L
FeCl3 2g / L
NaNO3 1g / L
Temperature 45-60°C
Time 20-40s
Pre-plated copper
CuCN 35-40g / L
NuCN 7-10g / L
Potassium sodium tartrate 30-40g / L
NaOH 15-20g / L
Dk 2-3A/dm2
Temperature 30-40°C

3. Precautions The operation must be rapid in all operations. The shorter the air stays, the better. Strictly electrified lower groove during electroplating, high current impact 3min when pre-plating copper. Before the aluminum part enters the acid bath to activate, its surface should not carry water, but should be dried;
Parts between processes must be cleaned.

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