I now use PPG DX520 and have used DuPont 5717s 224s for many years but they're not what you want to use for a de-rusting tank. It would cost you $1,000 to fill a 10 gallon tank up and they are usually a weak mix to begin with.
Ospho is one of those chems that contains phosphoric acid but it just converts the rust and leaves a nasty hard black crust on the metal that you can paint over. Besides, it’s about $40 a gallon in case lots.
Rust-Away is fairly expensive also at $33 a gallon. But, looking at the MSDS it says that it contains 75% phosphoric acid. So that might be a possibility.
What I’d really like to find is about 5 or 10 gallons of that Behr stuff in the old black jugs for $12 or $13 a gallon which is what I paid for it a couple of years ago.
Denny Graham
Sandwich, IL
