[Alan W]

I would use something like Bilt Hamber Hydrate 80 rust converter (description below).

Hydrate 80 Rust Converter

Traditional paints and coatings applied to corrosion give disappointingly short-lived performance because they simply hide the underlying and continuing corrosion - the failure is first seen by blistering of the coating and the rapid breakthrough of rust.

Hydrate 80 provides powerful protection to rusted steel surfaces, its electrochemical function stabilises existing corrosion by converting the iron oxides into a protective metal complex, it also combines with surface moisture and oxygen depriving the corrosion process of the conditions it requires. Paints and coatings applied to a Hydrate 80 treated surface demonstrate amazing improvements in long-term performance.

Alan W

 

[Alan W]

I've used various brands of Rust Converter over the years; such as Jenolite and two I can't remember the names of; all of which have worked well and prevented further rusting, although I've primed and painted the affected area afterwards.

I think Kurust was possibly one of the others you're thinking of.

Alan W