Rust occurs when the iron oxide in metal reacts with oxygen and water or air moisture. This "chemical oxidation" comes in varying degrees of rust damage identified as surface rust, scale formation and deep pits.
While rust corrosion is fairly common and can be troublesome, it can also be dealt with.
The first signs of surface rust are the appearance of a reddish-brown or reddish-yellow discoloration on iron or metal. As corrosion continues to the scale formation stage, it will soon form a layer of rust that starts to flake off.
With enough time, rust will begin to form deep pits and degrade any iron mass which can be particularly damaging and costly. Ultimately if untreated, this deep pits stage will lead to the metal surface's eventual disintegrate.
The good news is, corrosion of iron is preventable AND reversible.
Using a rust converter paint on a rusting metal surface will stop the process of corrosion. Rust converters chemically penetrate existing rust, reverse the degradation and leave behind a high quality latex metal primer.
You will know when the chemical conversion has taken place as the rust converter paints on milky white and dries black upon completion.
By sealing out moisture, using a rust converter extends the life of metal and prevents future corrosion from occurring. Your new surface will be rust proof.
The chemistry works like this:
A rust converter creates a permanent chemical bond, reacting with rust and converting it to a layer of magnetite; a black iron oxide mineral which does not react with oxygen or moisture.
Rust converters are also a metal primer and bonding agent for oil-based coatings (acrylic, enamel, epoxy, polyurethane and moisture-cured urethane) and waterbased coatings.
Effectively, once a rust converter is painted on to a rusted surface, rust is permanently converted, primed, sealed and ready for a topcoat.
You might have a rusted surface that you don't want painted -- if that's the case, you should use a rust remover instead of a rust converter. We wrote an earlier blog post on the key differences between a rust converter and a rust remover which might be helpful.