Grant Erwin writes:

So what's Evapo-Rust, and why would I want it?

Suspected to be a few cents worth of EDTA in water for $20/gallon. The
bottler won't be honest about what it is. The publish an MSDS that sez
nothing is in it that is hazardous. This in a world where water is
hazardous for MSDS purposes.

It's one of those things that 3M doesn't think is worth selling, but is
effectively hustled by a small outfit. Such as via newsgroup spam and
inflated "military" testimonials.

Really, what kind of technician relies on a product that has no scientific
basis, precisely because the maker won't tell you what's in it?