What is blackened steel?

A. I don't think that "blackened steel" is a codename or special industry lingo for anything, Ann; I think it really just means steel that has been blackened in some way. So "black oxided" may be as good a definition as any. In this process the steel is cleaned, acid activated, then dipped into a vat of hot strong caustic plus some nitrates or other oxidizers, which forms a black oxide product on the surface. While it's applicable to most any kind of steel, I don't think it's terribly durable or very rust resistant. So if you want a more durable coating you may need to specify a black nickel plating, black chrome plating, or zinc plating with black chromate conversion coating.

 Thank you Ted.