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Prove or disprove discoloration on 304L plate is rust

I have a proof case on some thin-gauge 304L nameplates that we had laser-etched with manufacturer's data.

I need a method to prove or disprove that the dark discoloration that was left after the laser process is rust/corrosion.

I think the discoloration must be indicative of some kind of corrosion reaction, since the laser essentially burns the information onto the nameplate.

Is HNO3/HF passivation an effective rust remover?

Will the change of the CuSO4 or Ferroxyl test tell me that my discoloration is 'rust'?

Matt Witherspoon
- Nashville, TN
2002

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Matt:

Yes, CuSo4 or ferroxyl tests will show you whether the discoloration is rust. It actually tells you that there is iron there, but if there is rust it will show positive for iron. Yes, HNO3/HF will remove the rust, along with some of the surface chromium, nickel, iron, etc. It probably will etch the surface slightly if that is okay. There are easier and safer ways to remove the rust than nitric/hydrofluoric.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2002