I've tried the gel version of Evaporust and would give it a 1 out of 5 rating. The first bit I got was too thick to even squeeze out of the bottle, and they sent me a new one, which I still wasn't impressed with. It might work OK for getting flash rust off, but for the flakes and more heavily rusted areas you'd find on a floor under the mat, a wire wheel is the ticket, NOT Evaporust. It has it's uses, but .....
Thanx for the heads-up. I haven't tried the gel and, now, I probably won't.