Sulfur and phosphorus heteroatom-containing compounds as corrosion inhibitors: An overview

Use of organic compounds containing nitrogen (N), oxygen (O), sulfur (S), and phosphorus (P) heteroatoms in their molecular structures is one of the most effective, economic, and practical corrosion inhibitors. The effectiveness of the heteroatoms toward metallic corrosion inhibition follows the order: P > S > N > O. The metal-inhibitor interactions involve the charge sharing between the heteroatoms and empty d-orbitals of the surface metallic atoms; therefore, a heteroatom with lower electronegativity value is more potent to form strong bonding (charge sharing) with metallic surface as compared to more electronegative heteroatom. Literature study reveals that almost all corrosion inhibitors have either one or more heteroatoms in their molecular structures particularly in the form of polar functional groups, which enhance their adsorption tendency on metallic surface. Present review paper features the collection of some major works that have been published on metallic corrosion inhibition containing these P, S, O, and N heteroatoms. Since now, several review articles have been published describing the application of N and O atoms; however, the reviews on use of P and S heteroatoms are scare. Therefore, aim of the present article was to mainly describe the collection of corrosion inhibitors containing S and P heteroatoms.