That may have been me back in February. I "won" the steel Commando tank on Ebay a few nights prior to that. My question was then how to re-rust/clean the inside prior to coating\sealing with either Caswell's and/or the POR kit.
Based on some of the replies and earlier digging around in the Forum files I went out and picked up some "Evapo Rust" over lunch yesterday. I took one of my (really, really) badly corroded chromed mounting brackets from my (now dismounted) luggage rack and dunked it into the solution until today about the same time:
Completely dissolved all rust, left all chrome (and leaves all paint) intact.
Needless to say, I'm now a believer. I use it on everything