Effectiveness of Rust Converters

Water and air cause iron to oxidize to rust.

Rust is formed when iron is oxidized from its native state to its reddish ferric or dark ferrous forms in the presence of water, heat and air. Chemical and physical products exist to either prevent or inhibit, but not reverse, rust formation.

Tannins

Rust converters don't reverse the rusting process to its pure form, but rather convert the iron to an inert compound which can't oxidize any further. Tannins, often in the form of tannic acid, are the most common chemicals used to convert iron to iron tannate. If too much is used, it will leave an acidic surface which can cause further oxidation; if too little is used, rust formation can continue.

Phosphoric Acid

Phosphoric acid converts rust to black rust which inhibits the further spreading of rust by forming a relatively inert substance called iron phosphate. The resultant thin layer helps prevent water and air from contacting the iron.

Physical Processes

Apart from chemically sequestering the iron, there are a number of physical processes such as sandblasting, etching, and electrolytic alkaline removal. However, they will only remove the existing rust, but won't prevent it from reappearing without adding a protective coating.

References

• Corrosion-Doctors: Rust Converters
• Rust Remover Tips And Tricks: Rust Converters