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"Rainbowing" and "Bluing" Stainless Steel


My hobby is modifying and customizing pocket knives for my personal use. The blades are typically stainless steel of various types. I would like to know how to "color" stainless steel as one would "blue" gun metal. Another interesting effect I've seen is giving the SS rainbow hues. It would be great to find out how I can do that. Will these same processes work on titanium and aluminum?

Thanks for your help,

Ed Acunzo
- New Orleans, Louisiana


Hi... even I am on the lookout for bluing stainless steel. We manufacture mugs, and are looking for a variety that could be provided by color on the metal. Since its a product of everyday use, I am looking for something that would be permanent and resistant to washing and scrubbing, and very importantly non-toxic. Thanks for the help.

Rishi Jain
- Bombay, India

Hello Ed,
Black oxiding of stainless steel is done industrially in a fashion very similar to black oxiding of steel, but with modified proprietary chemistry. If you know how to do black oxiding you could experiment on the stainless. Note that black oxiding is very dangerous because it involves strong caustic solutions at 230 deg. F. When water (which flashes to steam at 212 deg) is added to make good evaporation losses, there is a great potential for the solution to virtually explode.
Rainbow coloring of stainless steel can be done by a proprietary process called "Prismatic Finishing".
Although titanium and aluminum can be anodized, the processes are very different. The coloring in titanium anodizing is due to the formation of thin refractive films, but colors are applied to anodized aluminum with dyes.
Hello Jain,
Black oxide / bluing would be inappropriate for this application. The above-mentioned Prismatic anodizing might be appropriate though. Good luck.
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Ted Mooney, P.E. RET
Pine Beach, New Jersey
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