Q. Can stainless steel be colored and, if so, can you suggest a procedure for doing so?—Y.P.
A. Yes, you can color stainless steel. I addressed the same question in the September 2012 edition of Plating Clinic. Here is what I wrote at that time:
Yes, you can color stainless steel, but it is not a process that is typically performed in a plating shop. The basic process, which was developed by Inco (International Nickel) in the 1970s, is to immerse the stainless steel in a chromic and sulfuric acid solution at a temperature just below the boiling point of the solution. A thin layer of chrome oxide forms on the stainless steel, and by controlling the thickness of the oxide layer you can obtain colors that vary from bronze to blue, gold, purple and green. After treatment in this solution, the stainless steel is rinsed and given a cathodic treatment to harden the oxide layer. The layer can vary from 0.02 µm to 0.36 µm; the thicker the layer the darker the color. Most commonly, 304 grade stainless steel is used. The coating is reasonably robust but will scratch.
I am aware of one company that produces colored stainless steel, and you should be able to find others as well. Search the PFonline.com database using the term “coloring stainless steel” to find an article about another recently developed process.
Some artists use a lacquer-based process for coloring stainless steel which is good for decorative purposes but will not stand up to heavy use.