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Small Bubbles on Silver Plated Surface, Galvanic Corrosion?

Aluminum part used in electronics industry, part is plated with nickel, copper and then silver. The part has lots & lots of small bubbles on the top surface, upon removing we find a dark colored powder (?). This part was stored for several months in a non-controlled area, sub zero temps and the such. Is this in fact galvanic corrosion, can we determine why this happen, i.e., below zero temp, poor plating or some other reason. Also is there a fix for this problem other than the scrap bin.....

Perry Colpitts
- Moncton, N.B., Canada
2001

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2001

Before giving a considered response to your problem, please indicate the processes used to plate the part, i.e., was the Nickel electroless or electrolytic or both? Was the part baked during or after the plating cycle? What were the relative thicknesses of the various deposits? What was the preparation cycle used? What was the alloy used?

Regards

John Tenison - Woods
- Victoria Australia

Nickel is electroless , silver is electrolytic with a copper flash between. No bake, prep cycle unknown, alloy is aluminum (6061T6). relative thickness of products: nickel is min/5micro meters max/6.5m.m. , copper is flash/1.0m.m. , silver is min/7.0m.m. max/10.0m.m.

Perry Colpitts
- Moncton, N.B. Canada
2001