Boiler Corrosion Inhibitors

A corrosion inhibitor is any chemical compound that lessens the corrosion rate of metals or alloys when added to a liquid or gas solution. The National Association of Corrosion Engineers (NACE) further defines it as a “substance which retards corrosion when added to an environment in small concentrations”. The efficiency of corrosion inhibitor is caused by various factors including but not limited to: fluid composition, water quantity, and flow regime. A high efficiency (90%-99%) is guaranteed if the correct inhibitor and quantity are chosen.

Corrosion inhibitor works in several ways. One chemical mechanism is passivation, or the formation of a thin film on the surface of a material that inhibits contact of the corrosive substance -- preventing either oxidation or reduction. In cases of corroding materials, mechanism is done either through adsorption -- as a thin film on the surface of a metal, or scavenging -- inactivation of the dissolved oxygen. A lot of corrosion inhibitors are available in the market which includes hexamine, benzotriazole, phenylenediamine, diamethylethanolamine, polyaniline, nitrites, nitrates, cinnamaldehyde, chromates, phosphates, hydrazine, ascorbic acids, condensation products of aldehydes and amines, and a lot more. The suitability of a chemical to inhibit is dependent on the material of the system that they have to act in, the nature of the substances that they are added into, and their operating temperature. Failure to use a boiler corrosion inhibitor may lead to premature failure and excessive corrosion to the water system.