With increased use of iron and steel for building purposes today, Hydrated Iron(III) Oxide, or rust, has become a problem. Iron and most steels, given time, will rust. Rust is a reddish-brown solid that weakens the iron or steel and can cause it to break. Rust forms when iron is exposed to oxygen and water, the oxygen being found in the air, and the water being found in a variety of different forms, for example, rain, condensation and water vapour in the surrounding air.
Many different objects can suffer from rusting, and some examples include cars, bicycles, indeed, most vehicles, ships, buildings, kitchenware and bridges. In some cases, if rusting is not prevented, then there is a large risk of loss of life. If an important bridge was allowed to rust, then it could, after a period of time, collapse.
So, preventing rust has become a major issue today. There are many ways of preventing rust, and most rust prevention methods involve coating the iron or steel in question with a protective layer that keeps both water and the oxygen in the air from reaching the iron or steel. The most frequently used method of preventing rust is painting. Cars, bicycles and other vehicles are never seen today without a protective coat of paint. Care must be taken, however to paint over any chips in the paintwork, as even the smallest gap in the paint could allow rusting to occur. Paint also makes a vehicle look more attractive.
Other methods of preventing rust include placing a film of oil or grease over the iron. This must be frequently renewed and is normally used for moving machinery parts. Chromium, zinc and tin plating can be used, and these methods all involve using a protective coating for the iron. Zinc plating is also known as galvanising. Stainless steel has been developed, and it contains 10-25% chromium or nickel. Because of this, the steel will not rust. Sacrificial protection is sometimes used on ships’ hulls. Sacrificial protection involves attaching blocks of zinc to the iron or steel hull, below the waterline. As zinc is above iron in the reactivity series, it will corrode in preference to iron – the zinc blocks are sacrificed to protect the iron, hence the name “sacrificial protection”.
A final way of stopping rust from forming is to consider using different materials, for example wood could be used at times, where possible, in place of iron.
John Lenehan: Loreto College, Coleraine.
