Pyridine and its derivatives as corrosion inhibitors

Pyridine is nitrogen-based six-membered heteroaromatic compound having the molecular formula C₅H₅N. Pyridine itself and its derivatives are widely employed as corrosion inhibitors for different metals and alloys in various aqueous electrolytes. Substituted pyridine derivatives with electron-donating substituents offer strong bonding with the metallic surface and act as superior corrosion inhibitors compared to the pyridine derivatives without any substituent or with electron-withdrawing substituents. Nevertheless, pyridine derivatives containing either electron donating or withdrawing substituents at second and/or sixth positions show relatively high inhibition efficiency compared with the non-substituted pyridine and pyridine derivatives substituted at other position. This is attributed due to formation of highly stable chelating complexes by the pyridine derivatives substituted at second and/or sixth positions. Obviously, pyridine derivatives containing only one polar substituent, either at second or sixth positions, are behaved as bidentate ligands, whereas tri-substituted pyridine derivatives containing polar substituted at both second and sixth positions are behaved as tri-dentate ligands. Present chapter is designed to describe the anticorrosive effect of pyridine and its derivatives for various corrosion systems. Anticorrosive effect of various classes of pyridine derivatives has been described along with the various aspect of corrosion and corrosion inhibition.