Chapter 4 - Deep understanding of corrosion inhibition mechanism based on first-principle calculations

Abstract

Corrosion is a natural process that destroys the usable qualities of materials by reducing the binding energy in metals. Corrosion often known as rust, is an unwanted occurrence that degrades the luster and beauty of metal products while shortening their life span. Corrosion inhibitors play a most important role in closed environment systems. Corrosion inhibitors are inorganic or organic compounds that are dissolved in an aqueous medium. More efficient corrosion inhibitors are organic or inorganic compounds with elements from groups V B, VI B, or functional groups of the type amine, alcoholic, or carbonyl. Corrosion inhibitors are mostly classified based on electrode process, cathodic inhibitors, environment, mode of protection, etc., and their process of corrosion inhibition is via adsorption of corrosion inhibitors onto metals surface. Adsorption can be caused by electrostatic interactions between the adsorbed species, ionic charges or dipoles, and the electric charge on the metal at the metal–solution contact. The structure and functional group of the corrosion inhibitor, along with the presence of extremely loosely bound electrons, such as those found in anions, and neutral organic molecules with lone pair electrons or -electron systems coupled to multiple, particularly triple, bonds or aromatic rings, encourage electron transfer from the adsorbed species. Corrosion inhibitor molecule adsorption is frequently a movement process in which adsorbed water molecules are removed from the surface. In some circumstances, the adsorbed corrosion inhibitor may react with a product that is likewise inhibitive, generally by electrochemical reduction. An absorbed corrosion inhibitor may produce a surface coating that functions as a physical barrier, preventing ions or molecules from diffusing to or from the metal surface and thereby slowing corrosion processes and blocking reaction sites. The corrosion inhibitors are a highly active way of corrosion prevention and are used in commercial and industrial processes to minimize both the metal loss and acid consumption.