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Silver plating in barrel

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2006

Hello,
I am running a small electroplating shop and I am presently trying to silver plate electrical contacts in barrel. The contacts are 0.8 mm thick, area is 4 sqcm and are made of brass. Around 10% of silver plated parts have white or grey spots which are obviously related to the holes of the barrel. It seems that some of the pieces are stuck on the barrel during rotation. Still, I couldn't explain what occurs on a stuck piece and what causes emerging of the spots. What might be the explanation? What would be the solution for the problem?
Thanks for any help.

Nikola Adamovic
Galvanotehnik - Vrnjacka Banja, Serbia

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You need to use a barrel with grooves cut into the internal side of the barrel drum when plating flat parts, the soapy silver plating solution causes the parts to stick to the flat inner side and 'burnt' marks to appear on the deposit where the barrel holes are.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

2006