Metal Corrosion Types

High performance structural components often experience some form of corrosion, no matter what type of material is used. Good thing there are corrosion resistant coatings that can help increase the lifespan of a part, and reduce replacement and maintenance costs. However, in order to choose the right coating, it is very important to know what kind of corrosion a part is very prone to. Depending on how a part is used and what conditions it is exposed to, the type of corrosion that develops might differ.

5 Types Of Corrosion

Galvanic – This occurs if two metals with various electrochemical charges are linked through a conductive path. If metal ions move from the anodized metal to the cathodic metal, corrosion will take place. This type will also happen if one impure metal is present. When it contains a combination of alloys that has different changes, it can become corroded.

Stress-Corrosion Cracking – This can damage a component beyond the point of repair. If subjected to extreme tensile stress, the metal component can experience this. This type has different causes – this will include stress caused by thermal treatment, welding, and cold work. When these factors are combined with exposure to an environment that increases stress-cracking, the metal might suffer from irreplaceable damage.

Localized – This occurs if a small part of a component comes in contact with specific corrosion-causing stresses. The end result can be worse than the result of fatigue or stress since the small area corrodes faster than the rest of the component and that the corrosion works with other processes.

General – This happens as a result of rust. If metal like steel is exposed to water, the surface is oxidized. Hence, a thin layer of rust will appear. Similar to galvanic corrosion, this is also electrochemical. A preventative coating must interfere with the reaction in order to prevent oxidation.

Caustic Agent – This happens if impure gas, solids or liquids wear a material down. Though plenty of impure gases do not damage metal in dry form, they can form harmful corrosive droplets if exposed to moisture. An example of a caustic agent is hydrogen sulphide.