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Variable appearance in Black Oxide on SS

I would like to understand why parts that have been black oxided have such a variation in appearance, such as a smutty or chalky appearance compared to a cleaner appearance. Is this inherent to the process?

Jim Young
- Rochester, NY, US
2001

The smuttiness is inherent in some black oxide chemistries for SS. This can also be caused by inadequate activation before the blackening. Check the times of each step of the process to be sure of complete cleaning and activation. Some smuttiness can be minimized with the after-finish or by running the parts through corn cob real quickly.

Hope this gives you a place to start.

Dan Brewer
chemical process supplier - Gurnee, Illinois
2001

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