Most of us know rust as a reddish-brown flaky coat on metal and think nothing more of it, however rust is the term commonly used for the corrosion and oxidation of iron and its alloys, such as steel. Technically rust is Hydrated Iron (III) Oxide, also known as iron oxide (Fe²O³), as it is caused when iron reacts with oxygen and water - this reaction is known as oxidizing. If a piece of iron is left long enough, with exposure to water and oxygen, its rusting is inevitable - it could take days, weeks, months, or even years depending of the intensity of its exposure, however it will rust if it is not protected in any way. Rust is very common, as iron reacts easily with oxygen.
There isn't just one type of rust - there are in fact three different types of rust. Some are more common than others, but all can be prevented with the correct rust prevention or corrosion treatment methods. The different types of rust include:
• Pitting and cavity corrosion is a type of rust that occurs on unprotected steels used in infrastructure. The resulting pits can rapidly reduce the strength and thickness of a piece of metal; they vary from being narrow and deep to wider and shallow, neither of which are particularly good news!
• Contact corrosion occurs when a non-rusting stainless steel is in contact with another piece of metal that is rusting. It causes iron oxide deposits at the point of contact; however it can often continue to spread beyond this point.
• Crevice corrosion, a type of rusting that occurs (for example) in the gap between a nut and a bolt. It occurs in confined spaces (hence the name 'crevice' corrosion).
Changes in temperature, increased humidity (more moisture in the air for the reaction), and geographical elements (nearer the sea, windy sites, particularly rainy etc.) can all contribute to increased rust. This is made worse yet again by heavily salty environments, such as out at sea, due to the fact that salt can increase the speed of the reacting process.