Evaluation of zinc phosphate and zinc chromate effectiveness via AC and DC methods

This research is based on studying corrosion inhibitive effect of two anticorrosive pigments, zinc phosphate and zinc chromate. AC or electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (polarization) have been examined. At the first step, the pigments effects on electrochemical behavior of mild steel as bare metal have been studied in the presence of 3.5% (w/w) NaCl when saturated solutions of the pigments were prepared. At the second step, the pigments were dispersed in the epoxy resin. Electrochemical impedance spectroscopy of epoxy coated mild steel has been investigated when they were immersed in 3.5% (w/w) NaCl solutions. Coated mild steel at the same λ (λ is the pigment volume concentration to critical pigment volume concentration ratio) has been fitted for both pigmented systems with porous film model. The first and second steps comparison showed different mechanisms for the zinc phosphate when they were used in the solution and coating.