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Is electroplated hard chrome corrosion-resistant at all?
Dear Sir/Madam,
We have a technical difficulty in one of our research project and hope to get some help from you.
In one of our corrosion test, we used a carbond steel specimen partially plated with hard chrome. The reason we did that was to protect the unwanted surface from being corroded. Hard chrome was found not corrode at all during the test. After the test, however, we need to clean/descale the specimen (remove the oxides on the carbon steel surface that was not covered by the hard chrome) so that we could know how much the weight loss is. Unfortunately, during this cleaning process, we found we had lost more hard chrome than carbon steel oxide. In other words, although hard chrome did not corrode during the test, it was corroded during the post-test cleaning procedure.
We have checked with ASM Metals Handbook and found it is said the corrosion rates hard chrome in 10% and 20% NaOH should be nil at room temperature. In our cleaning, however, we found unbearable weight loss on the hard chrome (e.g. 200 MPY to 1,200 MPY, mils per year). We feel we have hit a ghost here. We had the hard chrome plated at a local company in sulfuric bath. Is this because they didn't do a good job ? Or the hard chrome is supposed to behave like that ?
We appreciate your expertised help on hard chrome plating.
Regards,
Fred Hua- Alliance, Ohio
First of two simultaneous responses --
Chrome is resistant to caustic soda solutions. BUT, Add in a small voltage and chrome is stripped very efficiently and is one of the two most common ways for stripping chrome in the industry. Possibly, you had it in a metal bucket/can or you had a very moderately dissimilar other metal in the bucket or ? In short, you somehow managed to have a battery.
James Watts- Navarre, Florida
Second of two simultaneous responses --
Are you also using anodic DC current to clean the parts?If so you are stripping the chrome from the steel.
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Todd Osmolski |
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