Gee phosphoric acid based rust converters are almost more trouble than they're worth. Paint on, then a bunch of the white powdery residue is left - have to remove that - which is an absolute PITA - apparently it can cause major issues with affecting your primer's ability to grip.

Then you also have to ensure you've washed off any acidic residue so it's not under the primer - as if you're using a zinc rich paint this can also have problems.

Found a recipe for a citric acid based one - for every 1L of water add 100g of citric acid and EITHER 40g of Sodium Carbonate (Washing Soda) OR 63g of Baking Soda. Also add a bit of detergent as a surfactant. Works ok - tad slower but more user friendly and no white residue.


Going to apply a bunch of paints in certain spots - fish oil in others where it's better suited.