LIQUID GUN BLUE - CHEMISTRY

[INTERPOLATE]

Greetings group.
Does anyone know anything about the chemical make-up of gun blue?
I have used it for years to identify stainless steel(a little bit on the end of a needle). Finally someone asked me questions about it and I had no idea.
Is there another way to quickly identify whether something is stainless steel or not?
Thanks!
DJ

[Cass]

Get the MSDS sheet on the gun blue. Use a magnet for stainless steel. At least the austenitic alloys are not magnetic. A grinding wheel will tell you something also.

[tonydacrow]

Interpolate,

If you're talking about "cold" gun blue, (as I assume from your use to quickly ID steel) they are usually solutions of selenium oxide. Hot blue uses lye and sodium nitrate in a super saturated hot water bath to create a hematite (Fe203 I believe)coating over the steel in a controlled rusting process.