www.frost.co.uk/fertan-iron-o...
Dealing with Flash Rust is a common problem with iron and steel and indicates that permanent corrosion will arise unless the flash rust is treated prior to further coatings. Fertan Rust Film Remover is the ideal product to remove corrosion. It is safe to use on painted and polished surfaces and is also excellent on tired galvanised surfaces. It carries out the rust removal process with no intervention necessary. The spray is easy to use and works in just a few minutes, gently removing rust film from your project. The colour changes to red when the cleaning is complete. Rinse with fresh water and dry completely.