Fabrication of heterocycles-inorganic materials for enhancing corrosion resistance

Abstract

Abstract Inorganic layers containing magnesium aluminate loaded with N-heterocycles were produced on Mg-3%Al-1%Zn alloy via plasma electrolytic oxidation (PEO) coating followed by organic dip coating. Imidazole (IA) and 2-aminoopyridine (AY) decreased the porosity and microcracks provided an organic coating layer, and thus inhibited magnesium corrosion well in corrosive environment. Organic molecules adsorption may be due to weak interaction between an electron donor from IA or AY having sufficiently low ionization potential and an acceptor, such as the coating surface, having sufficiently high electron affinity or unoccupied molecular orbitals. Quantum chemical parameters such as highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELOMO), and gap energy (∆E), dipole moment (μ), and the fraction of electron (∆N) were calculated using density functional theory. The theoretical and experimental results showed good agreement. Potentiodynamic polarization tests revealed that the inhibition efficiency ηp (%) improved in the following order: PEO coating (99.1%), PEO coating followed by IA (99.4%), and PEO coating followed by AY (99.9%).