The role of a zinc phosphate pigment in the corrosion of scratched epoxy-coated steel

The roles of a zinc phosphate pigment in the corrosion of scratched epoxy-coated steel were studied by means of electrochemical impedance spectroscopy, electrochemical noise measurement and scanning electrochemical microscopy. The experimental results of electrochemical noise measurement and electrochemical impedance spectroscopy revealed that zinc phosphate exhibited inhibition effect on the corrosion of the scratched epoxy-coated steel. The scanning electrochemical microscopy results implied that the scratched surface under zinc phosphate coating was re-healed by an insulating film. The mechanism of the inhibition effect of a zinc phosphate pigment was analyzed based upon the combined stochastic theory and shot noise theory using the Weibull distribution and Gumbel distribution function.