Copper residue on steel bolts. Corrosion problem?
Will a light, visible Cu residue on steel bolts (A286 material) eventually cause a premature corrosion or failure condition? We have some supplied steel bolts with a light copper residue left on them. The copper residue is the remains of copper coating which is used as a lubricant in a cold heading process. It is removed with a nitric acid solution. Some of the copper did not get removed. I am trying to find out if the bolt integrity will be at risk due to corrosion.
- Chicago, Illinois
It depends upon the environment. In 99 of 100 cases, there may not be a problem. However, nobody wants liability for the 1 failure. Unless every bolt will be used in an application where copper is not a problem (e.g., with anti-seize lubricant), I recommend cleaning in 45-55 vol% nitric acid at 120-130 F (QQ-P-35C [link is to free spec at Defense Logistics Agency, dla.mil]C Type VIII passivation solution).Ken Vlach
- Goleta, California
Finishing.com honored Ken for his countless carefully
researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work
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