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Hydrogen Embrittlement Failure in Chromium Plating
adv.
I work in a chemistry lab responsible for analysis of chromium plating baths. We also have a lab in-house that performs hydrogen embrittlement for process checks. Recently, we had a failure in the hydrogen embrittlement test, and yet our chemical analyses (Hex. Cr, Tri Cr, sulfates, surface tension and chlorides) show that it is within specification. One thing we have noticed is that the colour of the bath has changed. It is now almost black and you cannot see through it anymore.
Would anyone know a reason that would cause such a failure?
chemistry lab tech - Winnipeg, Canada
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First of four simultaneous responses -- 2006
Hydrogen embrittlement from chrome plating has little to do with the bath composition. High strength steels will always embrittle to some extent during hard chrome plating. Are you baking after plating? Bake should start within one hour of plating and continue 4 hours @
375F.
Dark color is a combination of trivalent chrome and metallic contamination especially copper and iron.
Jeffrey Holmes, CEF
Spartanburg, South Carolina
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Second of four simultaneous responses -- 2006
Possibly related, but not guaranteed. I strongly feel that more embrittlement is caused by the etch cycle than the plating cycle.
Dark color = one or more contaminants, probably metal, since you say that the tri is within limits.
I would look to see if there was another failure before I got too excited. I would hope that you have run one by now.
I used a porous pot from hard chrome plating consultants out of Cleveland for years. It is priced right and it worked well. It would drop the tri to low levels and it would remove most tramp metals. Bath would be close to original makeup color.
- Navarre, Florida
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Third of four simultaneous responses -- 2006
Dear Jennifer
check up with your iron levels. only that can turn your solution black.
all the best
Vikram Dogra
Irusha India - Chandigarh, India
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Fourth of four simultaneous responses -- 2006
Hi Jennifer,
the color which you do notice is caused by development of trivalent chrome, as more older the electrolyte get as darker the solution will be. Check the tri-chrome and keep it within the specs.
Regards,
- Mexico City, Mexico
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2006
Thank you all for your responses.
I think there is consensus (from this page and from our discussions in the lab) that it is most likely metal contamination. We currently do not have a method for the analysis of Cu and/or Fe in chromium solutions, however do have an ICP-OES that I believe would be capable of handling the testing. Does anyone have any other suggestions?
Chem Lab Tech - Winnipeg, Canada
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2006
Jennifer,
what also will be helpful is to measure the conductivity of the chrome solution, it should be above >350mS/cm, is just a quality test.
Regards,
- Mexico City, Mexico
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adv.