Quinoline and its derivatives as corrosion inhibitors

Corrosion inhibition using heterocyclic compounds, especially nitrogen-based, has been established as one of the most successful and admired methods. Quinoline is structurally similar to the naphthalene in which one of the carbons of aromatic ring is replaced by nitrogen atom. Quinoline has molecular formula of C₉H₇N that possesses 10-p electron in the form of five double bonds and one unshared electron pair of nitrogen atoms. Because of their high electron density, quinoline and its derivatives act as effective ligands and form strong bonding with the metals surface that comes out in the form of their high protection effectiveness. More so, quinoline derivatives containing heteroatoms at eighth position can form chelating complexes with the metallic atoms. Literature study showed that several derivatives of quinoline mostly substituted at eighth position are used as corrosion inhibitors. Some of the common substituents present in quinoline moiety that are tested are -NH2 (amino), -OMe (methoxy), -OH (hydroxyl), and -NO2 (nitro). Literature study showed that 8-hydroxyquinoline and its derivatives are most widely used corrosion inhibitors. Present book chapter aims to collect recent advancements in using quinoline and its derivatives as corrosion inhibitors. The chapter also explain the inhibition effect of quinoline and its derivatives, especially 8-hydroxyquinoles. Past, present trends, and future challenges of using quinoline-based corrosion inhibitors have also been discussed.