Improvement of the protective properties of the nanocomposite polypyrrole-Zinc oxide coating on mild steel by adding the dispersant sodium hexametaphosphate

This work reports on the use of the sodium hexametaphosphate (SHMP) surfactant for the dispersion of ZnO nanoparticles in the PPy polymer matrix for the production of the composite PPy-ZnO as an anticorrosive coating on mild steel. The coatings of PPy, PPy-ZnO and PPy-ZnO-SHMP were electrodeposited by cyclic voltammetry (CV) method. The anticorrosion behavior of all the coatings was studied in a 3.5% NaCl solution medium at room temperature. The performance of all the coatings was evaluated using polarization measurements, electrochemical impedance spectroscopy (EIS) and chronopotentiometry at open circuit potential (OCP). It was found that the presence of SHMP during synthesis resulted in a more homogeneous and compact coating in which the ZnO nanoparticles were more evenly distributed among the PPy particles. Furthermore the coating PPy-ZnO-SHMP exhibited higher corrosion resistance and provided better barrier properties compared to pure PPy and PPy-ZnO coatings. •Use of SHMP dispersant is proposed.•Nanoparticles of ZnO synthesized by potentiostatic electrodeposition.•PPy-ZnO composite coatings prepared by cyclic voltammetry method.•The presence of ZnO nanoparticles within PPy system significantly improves the physical barrier of the PPy-ZnO composite.•PPy-ZnO- SHMP coating exhibits the best corrosion protection performance in saline medium.