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Black oxided screws are rusting

I have recently designed an aluminum alloy case, Iridite + painted with black enamel for a small camera, and used black oxide steel screws to hold the top and bottom together. After 4 weeks of usage and travel (from canada to UK), the screws were all rusted (orange spots on the head of the screw). Is this normal? If not, could it be that the black oxide was not done properly at the screw shop? What is your recommendations? Regards, Gérard

Gérard Blais
system designer - Dorval, Quebec, Canada
2004

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Black oxide is reasonably corrosion resistant if and only if it is kept well oiled. It is therefore a high maintenance finish. I would tend to suspect that screws in a camera are not only not kept oiled, but any oil on them may even be deliberately stripped before assembly, leaving the finish highly susceptible to corrosion. A black plated finish like black zinc, black zinc-iron, or black nickel may be more appropriate.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004

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I will use black zinc, thank you very much!

Gérard

Gérard Blais
- Quebec
2004