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Rust on Black Oxide Parts

June 9, 2022

Q. Hello,
I am an engineer at a OEM equipment manufacturer. I have ran into an issue on one of our pieces of equipment that was shipped overseas. We are experiencing rust on several of our components that are from the same vendor of which the parts are black oxide coated. However adjacent parts from a different manufacturer with the same finish are not rusting. We have some of these parts in our inventory here since November 2021 and there is no rust present. We have not had any other issues with the black oxide with this vendor and when I questioned them about any possible changes to their process, they confirmed it is the same. My thought is that it is an atmospheric concern at the customers facility, as there was no rust reported when the machine arrived, but occurred 20 days after unpacking.

     

So my main question is: What would cause one part to rust and another part not to with the same coating? Any input is appreciated.

M Carter
- Robesonia, Pennsylvania