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Mill Scale Removal


Hi everyone.

We are trying to remove mill scale from steel prior to a powdercoat. What acid is the best to use for the removal of mill scale and rust? I seem to recall that Sulfuric acid is a good one for mill scale, but doesn't do the job on plasma edges. Just looking for some confirmation on my memory.


James Hanley
- Seattle, Washington



The "most pleasant" acid to use would be an inhibited phosphoric acid based pickle. It can be used in stainless steel eqpt and is compatible with the following phosphate process. It is also less likely to rust stain compared to the other acids. If by plasma scale you are referring to laser cutting, then there is no problem.

Roger Bridger
Walterisation UK Ltd - Croydon, UK


Hi, James,

Yes, you are right. Sulfuric acid is one of the common acids used to remove mill scale and the another is hydrochloric acid. The former is cheaper and efficient in the most case, but highly dense scale, such as plasma edges. The critical difference among both acids is working mechanism. Sulfuric acid penetrate per crack in scale layer and works underneath scale rather than dissolving scale and rust, but, on contrary, hydrochloric acid does.

Jun Zhang
- Cincinnati, Ohio, USA

September 14, 2011

I have a customer looking for a easy, quick test to determine if all the mill scale has been removed.

Joel Bialek
Sell Inspection Equipment - Lapeer, Michigan
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