Surface damage on a tank can be unsightly, but more importantly, it can hinder the optimal operation of your equipment. Understanding the various types of surface damage can help you better control and prevent them. Here is an overview of the three most common types:
Pitting
This localized form of corrosion appears as cavities on the surface. Pits can take different shapes, including narrow and deep, wide and shallow, or elliptical. In some cases, the pitting may undercut and run parallel to the surface. Chloride ions, which can be found in salts and bleach, are the primary cause of pitting as they damage the protective film on stainless steel surfaces. To prevent pitting, it is essential to control the pH, chloride concentration, and temperature in your workspace.
Corrosion
Corrosion can be caused by various factors, including the characteristics of the fluid flowing through the system and the environment in which the system operates. Similar to pitting, the rate of corrosion is influenced by pH, chemical composition, temperature, and fluid velocity. Environmental factors such as air temperature and humidity levels also contribute to corrosion.
The most common types of corrosion are:
General corrosion:
In this type of corrosion, the entire surface deteriorates, leading to the weakening of the material until it eventually fails.
Localized corrosion:
This includes pitting (as mentioned earlier), crevice corrosion typically found under gaskets and clamps, and filiform corrosion that occurs beneath painted surfaces, starting from small defects in the coating and spreading underneath.
Deformation
Deformation refers to the distortion and bending of the tank material, resulting in a shape different from its original structure. It can occur during tank fabrication when heat is applied. During welding, the material tends to warp and pull towards the heat source, especially around sharp angles. Deformation can also be observed during tank usage, such as when vacuuming, causing the sides to flex in and out due to changes in internal pressure.
