Don't Let Rust Ruin Your Life

Nobody likes rust, that annoying reddish, crusty stuff that collects on metal surfaces, but what exactly is rust and what causes it? Simply put, rust is the result of a chemical reaction between iron and atmospheric oxygen.

Iron isn't the only metal that reacts with oxygen, but it's the one that forms the dreaded rust from this combination. Iron, and even the iron in steel products, will rust faster in damper, humid climates as opposed to drier ones. What's happening is that iron oxide, the product of iron and oxygen, is a much larger molecule than the iron molecules. When the iron oxidizes, the new molecules require more space than the smaller original iron molecules and cause the surface to swell and sometimes flake off. Water only makes metal rust faster. Several causes are relatively high levels of dissolved oxygen, high salt content or certain bacteria that cause corrosion (iron or sulfate bacteria). Salt increases the conductivity of the moisture in the air and on the surface of the iron, creating more rapid rusting to occur.

The corrosion, or rust, is insidious once it starts. Some metal will crack, causing even more surface area to be exposed to the oxygen, thereby spreading the rust. Heat, as with most chemical reactions, tends to speed up the rusting process, so hot, damp, salty climates are the worst. Think of Miami in the summer.

Oxidation occurs with other metals, too, but these other materials have oxide molecules that are not larger than the original metal's, so it doesn't form a coating where the molecules swell. Aluminum oxidizes, but the oxide doesn't create an outer coating of large, flaky molecules, so the aluminum oxide actually makes an effective coating over the metal surface. The formula for iron oxide is Fe2O3 which makes the reddish rust we're all familiar with.