Organic corrosion inhibitors for industrial cleaning of ferrous and non-ferrous metals in acidic solutions: A review

Acidic media have been employed extensively in industry particularly during cleaning processes including industrial acid cleaning, acid pickling and acid-descaling. Hydrochloric, sulphuric, nitric, phosphoric and acetic acids are a few of the common aggressive solutions that are used for cleaning purposes. Several types of inhibitors are being employed for inhibition of metallic dissolution in acidic media in which use of organic inhibitors is one of the most frequent and economic methods. The presence of heteroatoms (O, S, N, and P) and π-electrons in the form of conjugation are among the most salient features of the organic inhibitors. These parts of the heteroatom containing molecules act as excellent inhibitors for metals and alloys corrosion in aggressive acidic solutions. This review article describes some recent major works in the field of metallic corrosion monitoring using organic inhibitors in acidic media. A literature investigation revealed that heteroatoms of these molecules exist in the form of polar functional groups which can actively participate in adsorption processes, in addition to the π-electrons of multiple bonds.