A comprehensive review of corrosion inhibitors employed to mitigate stainless steel corrosion in different environments

In view of the demand of the present day technology a wide variety of materials are being used for various industrial projects. The design engineer is responsible for selecting the appropriate material for each project. Aside from its physical properties, the choice of a material also depends on the mechanical and environmental conditions of the project. One of the most important factors that a project should consider is the propensity of the metallic structures from corrosion and their possible protection. In addition to other metals, stainless steel (SS) is widely used in various industries such as the petroleum industry and subjected to various processes such as acid pickling, descaling, and acid cleaning. Some of the common types of mineral acids used in these processes include hydrochloric acid and sulphuric acid which are very aggressive and may lead to corrosion if used as such. Various methods such as cathodic protection, application of protective coatings, corrosion inhibitors, or a combination of these have been used to prevent metal from corrosion. This review article targets different organic compounds used as inhibitors to inhibit SS corrosion in different corrosive solutions. The organic compounds which have already been reported in the literature as inhibitors include plant extracts, surfactants, amino acids, polymers, drug molecules, ionic liquids, and essential oils. The review gives a vivid account of the contributions made in recent years (2007 to 2022) based on the literature on the application of organic corrosion inhibitors for SS in various aggressive environments such as H2SO4, HCl, H3PO4, sulphamic acid, CO2, H2S, and NaCl at different temperatures. A perusal of literature revealed that most of the research on the corrosion inhibition of SS has been examined in acidic medium. Limited literature is available on SS corrosion ihibition in seawater condition, where SS suffers from localized corrosion such as pitting and stress corrosion cracking (SCC). Among various SS examined in the literature austenitic SS 316 has found more attention. Various research papers based on computational studies are also discussed in the review. The challenges and outlooks in this area of research have been pointed out with future directions proposed.