Types of Corrosion

There are several types of steel corrosion that can occur due to different mechanisms and environmental factors. Some of the common types are:

1. General Corrosion: This type of corrosion is uniform and affects the entire surface of the steel. General corrosion occurs when the steel is exposed to a corrosive environment, such as acid or salt water, and the metal ions start to dissolve.

2. Pitting Corrosion: Pitting corrosion is a localized type of corrosion that creates small pits or holes on the surface of the steel. This type of corrosion can occur in areas where the protective layer of the steel is damaged or in areas where there are different potential areas on the surface.

3. Crevice Corrosion occurs in small spaces or crevices, such as gaps between two steel surfaces. Corrosion occurs due to insufficient oxygen or the build-up of corrosive chemicals in the crevice.

4. Galvanic Corrosion occurs when two different metals are in contact with each other and exposed to an electrolyte solution. One metal corrodes more rapidly than the other, acting as an anode, whereas, the other metal acts as a cathode.

5. Microbial Induced Corrosion (MIC) is a type of corrosion caused by the activities and presence of microbes. This occurs in several forms and as a result, requires laboratory analysis to determine the type. The type cannot be determined on-site during an inspection of a vessel. This process of material degradation from bacteria can also be influenced by microalgae, inorganic, and organic chemicals. This form of corrosion can be destructive and requires specialist treatment processes to reduce its impact.

All of these types of corrosion can cause severe damage to steel vessels if left unchecked. This can pose a risk to safety, and maintenance costs, including repair or replacement of the affected steel components.