As Rudy says, there is stainless and stainless and there is rust and
rust. Most stainless steels are very sensitive to halides (hence Rudy's
remarks about hydrochloric acid). Many (most) water-soluble fluxes
contain organic hydrohalides which decompose at soldering temperatures
to form hydrogen halides, which, in the presence of water (from the
atmosphere) form hydro-chloric or -bromic acids, which will attack most
stainless steels, even high nickel/chromium ones containing molybdenum,
such as 18/8/2. You are probably therefore right concerning flux
residues, which should be well washed off to avoid trouble.

You may not know it, but even very pure water will attack stainless
steel, producing "red plague". In fact, this is a fine iron-rust powder
that adheres to the surface, but can be wiped off. Tap water will not do
this.

Brian

Ken Patel wrote:
> Chemical Expert,
> Can stainless steel RUST can be easily cleaned from a sheet metal of tested
> assemblies? Cause of the RUST looks like is water soluble FLUX. We do not
> want to remove the boards from a sheet metal. Per my supplier Stainless
> steel should not rust but...
>
> re,
> ken patel
>
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