Corrosion is defined as the deterioration of a material as a result of chemical reactions between it and the surrounding environment. Although corrosion affects a variety of materials including polymers and ceramics, the term is most often associated with the degradation of metals.
In a 2016 study conducted by the NACE (formerly known as the National Association of Corrosion Engineers) and outlined in their publication “The International Measures of Prevention, Application and Economics of Corrosion Technology (IMPACT),” corrosion incurs a global cost of $US 2.5 trillion dollars. This figure represents roughly 3.4 percent of the global Gross Domestic Product (GDP).
The Most Common Types of Corrosion
Corrosion consists of a series of usually complex chemical reactions and may be initiated by several different mechanisms that are dependent on the surrounding environment. This has given rise to the various classifications of corrosion.
All corrosion is not equal. The key to effective corrosion prevention and mitigation lies in a basic understanding of the type of corrosion being dealt with and the factors that are responsible for its formation. In this article we will look at the most common types of corrosion and explain the underlying mechanism of each.
Uniform Corrosion
Uniform corrosion is the most common type and is characterized by attacks over the entire surface area of the metal exposed to a corroding agent. This type of corrosion is typically caused by chemical or electrochemical reactions that cause the metal to be consumed while forming oxides or other compounds over large visible areas. These reactions cause the metal to lose thickness over time and can continue until the metal has been dissolved entirely. (Discover how the aviation industry deals with this type of corrosion in Detecting and Treating Uniform Corrosion in Aircraft.)
Galvanic/Bimetallic Corrosion
Bimetallic corrosion, also known as galvanic corrosion, is the corrosion that occurs when two dissimilar metals are directly or indirectly in contact with each other. Visually, this type of corrosion is characterized by the accelerated deterioration of one metal, while the other remains unaffected.
Read more: The 8 Most Common Forms of Metal Corrosion
