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topic 18748

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.


Kelly Kane
- 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,]C Type VIII passivation solution).

Ken Vlach
- Goleta, California
contributor of the year honored Ken for his countless carefully
researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work
which the finishing world continues to benefit from.

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