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Blisters on Nickel-Chrome Plated Articles

We cast several different items in zinc alloys many of which are nickel-chrome plated. We have noticed sometimes that the plated pieces develop "blisters" after about 4-5 days from plating. We have taken care to clean the substrate throughly including the normal electrolytic cleaning prior to plating. The blisters do not develop on all our castings, just a few odd ones. This is a source of worry as we would not like to deliver the items with the fear of it developing blisters later.

I shall greatly appreciate anyone giving me a solution to our problem.

Aloke Mookerjee
- New Delhi
2000

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Aloke. Did you start with a copper deposit before nickel? Try to bake after chrome to remove hydrogen. Regards Anders Sundman 4th Generation Surface Engineering Consultant - Arvika, Sweden Hi Aloke, Your problem does not seem to have anything to do with your pre-plating cleaning cycles.It appears to be problem with your casting which have microporosity.Please heat the items at a temperature above 80 to 100 °C.Check out for blisters. Bye, Ravindra Sant, Mumbai Ravindra Sant - Mumbai, India

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Thank you both Anders and Ravindra for the advice. Anders I do copperplate (alkaline followed by acid copper). Any additional advice would be appreciated. Ravindra, when do I heat the items - after plating or before?

Regards

Aloke

Aloke Mookerjee
- New Delhi
2000

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Aloke.

Do the bake before and after plating 200 °C for two - four hours.

good luck to you

Anders S

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden
2000

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Aloke

All Info so far is correct, But you did not say where the blisters are Between base material and copper; between copper and nickel; or nickel and chrome.

If nick is over brighten and/or PH is incorrect internal stresses could be part of the problem. Bake will help

Chris Snyder
plater - Charlotte, North Carolina
2000