Rust Death #1 35% Phosphoric acid 65% water. (Commercial grade Phosphoric is typically 70% so 1 litre of this with 1 litre water gets you there). Use this for mild applications or where it can't be rinsed off the parts. Rust Death #2 35% Phosphoric acid 65% water as above, plus 5ml Nitric acid per litre of solution. More aggressive, must be rinsed off, best not to use this on chrome pieces. You got BAD rust, this is the stuff.