If left untreated, rust not only detracts from the appearance of metal surfaces but actually weakens the bonds of the metal itself. It can render structures unsafe and machinery unusable. So it's absolutely critical to remove rust from metal and protect it to inhibit or prevent the recurrence of rust.
Awareness is the first step in the battle against rust. You need to know how rust works.
The inescapable fact is that metals are unstable in most environments. The moisture and oxygen that allow life is a poisonous environment for metals. The temperatures and moisture levels that occur in everyday life is enough to cause metal to rust.
To get usable metal out of ore requires the application of considerable amounts of energy that change the chemical structure of the metal. Once the metal is pure enough to be tooled, it is at a state where, in simple terms, it wants to return to a lower energy state by combining chemically with other elements. This is most commonly oxygen.
When metal molecules come into contact with water molecules, they give up electrons, becoming positively charged in the process, creating an electro-chemical reaction that leads to the creation of an oxide. This "battery-effect" charges any corroded spot so that it is ready to interact with other molecules, which is why rust spreads if it's not actively contained.
Rust can be confined to a single spot or spots, causing pitting, or along a crack or over a wide area. Any area of rust, even a single pit, provides the seed point for further corrosion, with the chemical interaction spreading wider.
Though the rusting of steel is the best known example, this happens in all metals, even ones such as aluminium, where the effects of corrosion is perhaps not as clearly visible.
Factors such as the acidity or alkalinity of the environment affect the ease with which rust develops, as does
- high temperature,
- temperature variation,
- friction between surfaces,
- internal stresses in the metal, and
- even the action of biological organisms such as anaerobic bacteria.
Rust can best be controlled by thoroughly cleaning surfaces, removing all vestiges of the rust (for instance by abrasive blasting) and then applying a suitable protective coating.