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How many times can cadmium and chrome be stripped?

Does anyone know ? How many times that cadmium and chrome could be stripped for high strength steel 4340. There is no comment on AMSQQP416 and QQ-P-320 .

Thanks!

Tony Hwa
- Kaohsiung, Taiwan
2003

Cadmium can be stripped a great number of times with ammonium nitrate with no ill affects that I am aware of. Chromium is another story.The harder it is the less it should be stripped. If I remember correctly, anything above Rc 39 is supposed to be baked for Hydrogen de-embrittlement before replating. I am not aware of any generic limit if you follow the rules on baking. Some manufacturers will have limits. The more critical the use, the more stringent the rules become, with good reason.

James Watts
- Navarre, Florida
2003

I agree with James in that Cad is relatively safe to strip as many times as needed. About chrome, it is highly probable that if striping is done by immersion in HCl this will induce hydrogen and dictate a heat treatment for every replate cycle. Fortunately, chrome can also be stripped more safely by a reverse cycle in caustic soda [affil links] which eliminates hydrogen impregnation and will not adversely attack the surface of steel. You didn't mention your base material, but both methods will attack other non-ferrous materials such as aluminum, brass, etc. I think the answer mostly depends on the particular application and has to be agreed upon with your customer.

Guillermo Marrufo
Monterrey, NL, Mexico
2003

This sounds like an aerospace question. Inquire of the mfg. They will guide you on cycle life.

Jon Quirt
- Minneapolis, Minnesota
2003