Corrosion electrochemical behavior of epoxy anticorrosive paints based on zinc molybdenum phosphate and zinc oxide

Electrochemical impedance spectroscopy (EIS) was applied as a principal too l to describe the efficiency of anticorrosive epoxy paints (primers) based on zinc molybdenum phosphate (ZMP) pigment. Steel-coated samples were expos ed to a 0.5 M NaCl solution. During the study the corrosion potential (E-oc ) and R-p values also were monitored every 24 h. It is discussed the incorp oration of micronized ZnO (1 I-Lm) pigment to the base mixture and its posi tive, reinforcement effect on the protective properties of ZMP primer. The explanation is related to the izoelectric point (IEP) of ZnO particles (pH < 9), which determines their positive surface charge and electrostatic attr action with the molybdate anion. In this case the charge of the formed doub le layer capacitor is very high. Moreover, the mentioned attraction inhibit s and saves ZnO particles from their rapid dissolution to hydroxide. (C) 19 99 Elsevier Science S.A. All rights reserved.