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.

There is another form of iron oxide known as black oxide or black rust that isn't harmful to the iron. This colors the metal, but since the molecules aren't any larger than the iron, it doesn't form the rusty corrosion that eats into the metal. This black oxide can be found on some tools like drill bits and the bluing on guns. To create the black oxide coating, the metal can be heat treated until the black oxide, Fe3O4, forms.

Now back to the harmful rust. Once it's started, there are several ways to stop it, but understanding how it's spread is necessary so you can have a good understanding of why you're doing what you're doing. In the rust is oxygen that is capable of moving into the metal to cause deeper seated rust. The best way to eradicate the rust is to dissolve it or convert it into the black oxide. Certain acids in rust removal products can melt away the rust and help convert it to black oxide or you can always scrape away the rust manually and then coat it with an oil or cream.

There are numerous ways to try to prevent rust from occurring in the first place, such as coating iron materials with certain oils or waxes. One method most people have heard of is galvanizing. This is the process of coating the metal with zinc and is named for Luigi Galvani, it's discoverer. When the zinc covers the iron, the zinc gets oxidized instead of the iron, preventing rust, however, if the zinc coating becomes worn or is scratched off, the iron underneath will become exposed to the oxygen and corrosion will start. Another method to prevent rust is to make sure the product is surrounded by the fumes of a corrosion-inhibiting material such as camphor (moth balls) or a product that absorbs moisture in the air. Anything that prevents moisture from interacting with the iron will also work, so if the material is packed up tightly in a wooden box, it should be protected against corrosion.

So as a parting word on rust, it may be a nasty part of life, but with a little care, diligence and luck, it won't ruin your favorite tools or cause you to spend your paycheck at the local hardware store.