Relationship between corrosion protection and cathodic disbondment resistance of the epoxy-zinc phosphate coating

Abstract

Epoxy coating containing zinc phosphate [Zn₃(PO₄)₂] ratios varying from 0, 10, 20 and 30 % were prepared and studied for wet adhesion, anti-corrosion and cathodic disbonding resistance. The coating anti-corrosion properties were investigated and evaluated by Electrochemical impedance spectroscopy (EIS) and salt spay test. The results show that pigment zinc phosphate ratio of 20 % and 30 % improved the anti-corrosion, wet adhesion strength and cathodic disbonding resistance for epoxy coating. The study also showed that the anti-corrosion inhibitory ability of zinc phosphate is related to the resistance to cathodic disbonding due to the formation of complex films that reduce the cathodic protection current at the defect of the coating.