Epoxy coating anti-corrosion properties enhancement via the steel surface treatment by nanostructured samarium oxide-poly-dopamine film

Abstract

Nowadays, the rare earth element-based conversion coatings (REE-based CCs) are a potential eco-friendly alternative for hazardous and carcinogenic Cr-based CCs. These coatings have morphological defects that impair their performance; therefore, they need to be surface modified.In this study, for the first time, the steel surface was coated with an eco-friendly Sm-based CC and then post-modified by poly-dopamine based biopolymer. The air-exposed based self-polymerization and oxidant-induced polymerization are two protocols which have been utilized for poly-dopamine synthesis. The SEM/EDS analysis and Raman spectroscopy have been employed for the treated steel surface characterization. In addition, the electrochemical impedance spectroscopy (EIS) analysis and salt-spray test (SST) were carried out to investigate the epoxy (EP) coating corrosion protection performance.The Rt values of the EP applied on the Sm-PDA modified steel, subjected to a 3.5 wt. % NaCl solution, are respectively 2550 GΩ.cm2 and 100 kΩ. cm2 before and after the creation of scratch. These values are about 94000-fold and 21-fold more than the Rt of the defected/un-defected EP coatings applied on the unmodified steel. In addition, the EP applied on the Sm-PDA modified steel showed lower corrosion and less disbonding in SST and higher resistance against CD than the EP applied on the unmodified steel.