Corrosion is a natural phenomenon where metals return to their natural oxide state. Carbon steel is among the easiest metal to corrode but due to the economic it is also the most common metal used in the industry. Corrosion in the cooling water system can be of many categories. It can be of general flash corrosion due to the natural presence of anode and cathode, under deposit corrosion underneath deposition, crevice corrosion, galvanic corrosion, and microbiologically induced corrosion.
The method chosen for corrosion control is mainly based on the make-up water chemistry. If the make-up water is considered soft or low in calcium, the corrosion inhibitors selected will generally be of inorganic types. It either can be a low concentration of zinc or molybdate, which is not classified as heavy metal combined with organic and inorganic phosphate. In the absence of calcium, these inhibitors are readily capable of providing sufficient protection.
In the presence of high hardness water, corrosion inhibition selection will generally favor the full application of inorganic and organic phosphate or organic phosphate alone. In the presence of calcium corrosion inhibition means will be provided with a minimal potential of scales formation.