Phthalocyanine, naphthalocyanine and their derivatives as corrosion inhibitors: A review

Phthalocyanine and naphthalocyanine are important classes of nitrogenous based five-membered heterocyclic compounds in which benzene and naphthalene moieties are fused with porphyrin structure, respectively. Because of the presence of four nitrogen atoms with free unshared electron pairs and various aromatic rings with extensively conjugated π-electrons, phthalocyanine, naphthalocyanine and their derivatives are assume to form strong chelating complexes with metallic atoms. Because of their this property these compounds act as excellent anticorrosive materials in aqueous as well as coating conditions for various metal/electrolyte systems. Present review article aims to collect the past and present advancements on phthalocyanine, naphthalocyanine and their derivatives as corrosion inhibitors. Though outcomes it can be seen that these compounds become effective by retarding both anodic and cathodic reactions and mostly behaving as mixed-type inhibitors. Adsorption of phthalocyanine, naphthalocyanine and their derivatives mostly followed the Langmuir adsorption isotherm.