Rust converters, why ?

[MetalMonkey]

Phosphoric acid works about as well as anything you can buy - if you can get hold of it since they banned the high concentrate solutions. Dilute with water and mist it on with an old spray bottle.
There is also a thread on here about a rust treatment based on citric and bi carb, this also works well, but is more of a "dipping" solution.

Remove as much of the rust mechanically or via blasting as possible first, nothing will work on flaky rust.

Don't bother with hammerite metal type paints - Epoxy it and then coat with a 2K or underseal of your choice.

 

[Morris]

Phosphoric acid works about as well as anything you can buy - if you can get hold of it since they banned the high concentrate solutions.

I've just bought it at 45% concentration from a company called Valet-Chem. Best I could find before was 50% so not too agreed.

 

[addjunkie]

Look for navy steel, or blue steel.

 

[Gareth J]

Controversial opinion; rust isn't the baddie and removing every last iota is a waste of energy/time.

Water/air/salts are the enemy. Rust doesn't need old/unremoved rust to breed from, like an infection. New steel rusts with no previous rust colony.

Yeah, it's important to remove surface rust and definitely flaked rust. But only so as you can get a good key and seal using whatever is needed to seal out the elements. That's more achievable on steel that doesn't have loose rust on it. It also needs to be dry or you'll potentially seal in a pocket of potential rust (water/air/steel) that'll have the resources to push a protective layer open. That's really hard on seams and very badly pitted steel. Here a rust converter might be of value as it clears flaked rust away and lets the surfaces be dried effectively while giving a good key for the new protective layer.

Maybe...