Chapter 6 - Corrosion Inhibitors

Abstract

This chapter discusses various corrosion inhibitors and neutralizers and their application in petroleum industry. Corrosion and scale deposition are the two most costly problems in oil industries. Corrosion inhibitors have been divided into many groups, such as: cathodic and anodic inhibitors, inorganic and organic corrosion inhibitors, or filming and nonfilming inhibitors. From the chemists's point of view, corrosion inhibitors can be classified into the following broad groupings: amides and imidazolines, salts of nitrogenous molecules with carboxylic acids, nitrogen quaternaries, polyoxylated amines, amides, imidazolines, and nitrogen heterocyclics. Low molecular weight corrosion inhibitors often change the surface tension of water. These groups act as surfactants, since they form a protective layer on the metal surfaces. Polymeric corrosion inhibitors act in the same way as ordinary low molecular weight inhibitors. Polymeric film-forming corrosion inhibitors differ from polymer coatings as they exhibit a specific interaction with the surface before the dry film is formed. Corrosion problems may occur in numerous systems within the petroleum industry. Many anticorrosion compositions involve environmentally dangerous products, such as chromates, fatty amines of high molecular weights, imidazolines, etc. The use of some of the alternatives, for instance, polyphosphate or polyphosphonate, is limited because they precipitate in the presence of the salts of alkaline earth metals, or because of their high costs.