Cleaning Rust from Cold-Rolled Steel

Question:

How can we clean the rust off of unpainted cold-rolled steel parts slated for electrocoating that underwent an atmospheric corrosion attack from an accidental release of muriatic acid vapors in our plant? This is a real-time nightmarish problem that I think other manufactures have faced. What are other chemicals besides muratic acid that need to be banned from our sheet metal fabricaion plant? A.H.

Answer:

You don't describe the degree of rusting, but I can imagine it is pretty great. I am also not aware of what processes you readily have at your disposal in your plant. It is sometimes easier to job out work such
as this if you are not properly equipped. Given the degree of rusting that I believe will be present on these parts, shot or sand-blasting may be an effective alternative for cleaning these parts.

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You could also pickle parts in an inhibited sulfuric acid tank followed by thorough rinsing and possibly a rust inhibitor. This will remove most of the rust with minimal base metal attack. You need to assess which is easiest for you and most cost effective.

It is hard to answer your second question without knowing what else is in your plant. The bottom line is that it is impractical to ban all chemicals from your plant for fear of a repeat of this problem. High humidity will also cause your steel to rust, yet there is no practical way that you can eliminate it. So to ban all process chemicals that may create rusting is probably impractical and unnecessary.