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Why does steel rust?

Rust can be quite damaging

Steel is one of the most popular building materials in the world and is used in both in homes and industrial buildings everywhere. However, there is one major issue with steel-- it's high propensity for rust. In order to get the most out of steel it is important to understand why this material rusts and how to prevent it.

Rusting Away- Steel's Tragic Flaw

It is not uncommon to see famous bridges and historic buildings turning the familiar dark brown and dingy red of rust. When a structure is made of steel or even another metal, it will rust if it contains any iron. When iron is left exposed to water and oxygen, it will go through a process called oxidation.

In order to understand the oxidation process, you will need to know a little bit about chemistry. All elements after helium on the periodic table need to have 8 electrons in its outer shell If an element does not have 8 electrons, it will borrow electrons from different elements to reach that level. Through a reduction reaction, rust is created.

Rusting Away

When steel starts to rust, this specific chemical reaction is called corrosion.

When the steel is exposed to water and air, various types of rust may form. The most common type of rust is Fe203.  Rust will only develop on the outer part of a surface since the metal structure needs to be exposed to water and oxygen.

This means that structures that are submerged in water, are around water more often or are created specifically for use in water are more prone to rust. However, when a metal structure is submerged in water, it does not rust as quickly since the presence of oxygen is not as prevalent as it is above ground.

When a metal structure is in saltwater rather than freshwater, it will rust faster. Salt will accelerate the corrosion process and will cause rust to form more quickly. Salt’s corrosive nature makes rusting a problem in colder climates as salt is commonly used to melt snow. The salt may cause cars, bridges, roads and other steel structures to deteriorate faster than normal.

As with any material, nothing will last forever. Rusting is just another way of nature reminding us that all things eventually deteriorate. Take care to properly store and clean your steel tools and surfaces if you want to keep them in good shape for as long as possible.

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