Corrosion Protection of Mild Steel Using ZnO/NiO Pigment-Based Epoxy Coating

The ZnO/NiO pigment was prepared by solid-state reaction and examined by using x-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Visible spectroscopy. The paint containing the pigment was applied to a mild steel substrate and its electronic behavior was investigated using the Mott-Schottky method. The corrosion resistance of the paint was assessed by utilizing electrochemical methods. The Mott-Schottky plot implies that the ZnO/NiO-based painted mild steel sample revealed p-n-type behavior, and exhibited higher open circuit potential values than bare mild steel and epoxy-painted steel, owing to the effective barrier ability of the ZnO/NiO pigment. The rate of corrosion for the ZnO/NiO-based painted mild steel in 3.5 wt.% NaCl was 0.02 mpy, which was significantly lower than that of bare mild steel and epoxy-painted mild steel samples, respectively. Electrochemical impedance measurements supported corrosion rate measurement results. The excellent corrosion protection found in the case of the ZnO/NiO-based painted mild steel sample can be attributed to the incorporation of the pigment, which improves the barrier effect and inhibits charge transfer owing to p-n junction formation. No primer or barrier coat is required once the ZnO/NiO-based paint is applied on mild steel.