It is very common for metallic industrial components to experience corrosion during their lifetime. This is because they are frequently exposed to harsh environments. Thus, various types of corrosion resistant coatings are used to avoid the corrosion. These coatings help improve service life of the metallic parts, as well as reduce maintenance costs. Most anti-corrosion coatings are developed to address five types of corrosion – galvanization, localized, general, stress, and caustic agent corrosion. This post offers information on the five types of corrosion, as well as various popular anti-corrosion coatings.
Explanation on Five Types of Corrosions Affecting Metal Components
The choice of the right anti-corrosive coating will depend on your understanding of these five types of corrosions.
- Stress Corrosion Cracking (SCC): This type of corrosion can damage a metallic machine component beyond repair. A metal component may break down under extreme tensile stress. Thus, cracks start appearing on its sides, which leads to corrosion. There can be multiple reasons of SCC such as welding, cold work, and thermal treatment. All these factors combined with harsh environment lead to stress-cracking.
- Localized Corrosion: As the name suggests, this type of corrosion affects small part. It may be due to exposure to certain environmental elements or stress cracking. In this situation, a small area will corrode faster than other areas. In addition to that, the corrosion aggravates due to fatigue and stress. However, the end result is always worse than a single effect of stress or fatigue.
- Galvanic Corrosion: This is another common form of corrosion after general corrosion. Also, some industry experts consider it a more common form of corrosion. This corrosion is initiated when the metal parts with different electrochemical charges are linked to each other through direct contact or a conductive wire. Corrosion occurs when cathode ions move from the anodic metal to the cathodic. This corrosion may also occur, if an impure metal is involved. For example, if an alloy is made from different metals of different charges, then corrosion may affect one of the metals. Mostly, the anodized metal is weaker, and loses its ions to cathodic metal. Generally, corrosion resistant coatings are applied to prevent the transfer of ions causing corrosion.
- General Corrosion: This is one of the well-known forms of corrosion that occurs due to rusting. When a ferrous metal is exposed to moisture, the oxidation occurs, due to which a thin layer of rust appears on its surface. This corrosion is electrochemical, and can be avoided by using a suitable anti-corrosive coating.
- Caustic Agent Corrosion: This form of corrosion occurs when a metal comes in contact with solids, liquids, and impure gases. It is said that most impure gases don’t cause corrosion. However, if they come in contact with water droplets, corrosive, and toxic water droplets are formed. One of the examples of caustic agent is hydrogen sulfide.
Hence, before choosing what type of corrosion inhibiting agents your application requires, you need to identify the type of corrosion affecting a particular metal part. In the next installment of post, we will discuss various types of corrosion resistant coatings. Microsurface Corporation in San Jose, California is one of the leading and well-known applicators of engineered lubricants, coatings, and manufacturer of Timesaver Lapping Compounds.