Corrosion is a natural process that occurs when metals react with oxygen and form metal oxides if left unchecked will lead to permanent loss of assets. All water contains some dissolved oxygen and is therefore somewhat corrosive. The rate of corrosion depends on many factors including the water’s pH, electrical conductivity, oxygen concentration, and temperature.

In chemistry, a corrosion inhibitor or anti-corrosive is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy, that comes into contact with the fluid. The selection of a corrosion inhibitor depends on the Cost of the inhibitor. Inhibitors should be environment friendly and have extremely low toxicity to living organisms The nature of the corrosive inhibitor depends on (i) the material being protected, which are most commonly metal objects, and (ii) on the corrosive agent(s) to be neutralized. 

Chemical Treatment

Treatment of corrosive water can be either chemical or physical. Chemicals used in the treatment are either meant to stabilize the water, form a protective film on the pipe surface, or kill problematic bacteria. The corrosion inhibitor can be classified as anodic, cathodic, mixed, or general filming types. They are typically film-forming compounds that cause the formation of precipitates on the surface blocking both anodic and cathodic sites indirectly. Anodic inhibitors are, for the most part, dangerous inhibitors, especially if their concentrations are too less. But cathodic inhibitors are generally safe. 

Known applications

Benzotriazole inhibits the corrosion and staining of copper surfaces. Corrosion inhibitors are often added to paints. A pigment with anticorrosive properties is zinc phosphate Disinfectants are used to counter microbial corrosion. Benzalkonium chloride is commonly used in the oil field industry. In oil refineries, hydrogen sulfide can corrode steels so it is removed often using air and amines by conversion to polysulfides. Orthophosphates along with zinc may be added in water treatment systems to prevent corrosion in cooling water treatment Volatile amines are used in boilers to minimize the effects of acid. In some cases, the amines form a protective film on the steel surface and, at the same time, act as an anodic inhibitor. An inhibitor that acts both in a cathodic and anodic manner is termed a mixed inhibitor.