[Timothy Terwilliker (OP)]

what is the name of the chemical that is in evapo rust

[chiralSPO]

It appears that this product is composed of three compounds: water, a chelating agent and a detergent. Unfortunately, they are keeping the formulation as a proprietary trade secret. Based on the sds, it appears that the product is slightly acidic (6 <pH <7), and is fairly non-toxic, and only produces CO, CO₂ and H₂O during combustion. (see here: https://images.homedepot-static.com/catalog/pdfImages/94/94e4d2be-a874-46f2-9a69-739e0fa09231.pdf )

I would guess that the chelating agent is a partially deprotonated (self-buffering) poly-acid (for example, a mix of dibasic and tribasic citrate would buffer at a pH of about 6.4, and would likely be an excellent chelating agent for iron, and would be edible).

The detergent could be something like choline (cationic) or a deprotonated fatty acid, like laurate (anionic) or betaine (neutral, zwitterionic).

That's all I got...

[Bored chemist]

By far, the largest concentration of a chemical in that product is water.

Laurate would fall out of solution at that pH. I'd guess at the surfactant something like sodium laureth sulphate or whatever is cheap these days.

According to this
https://www.engineeringtoolbox.com/density-aqueous-solution-formic-lactic-oxalic-acetic-citric-acid-concentration-d_1953.html
 the density is about right for citric acid solution so a citrate buffer is plausible. though that's not very strong evidence.