Corrosion resistance of inorganic zinc-rich coating reinforced by Ni-coated coal fly ash

Abstract

To recycle the solid waste coal fly ash (CFA), a new approach of adding Ni-coated coal fly ash (Ni-CFA) to waterborne inorganic zinc-rich coatings (ZRCs) was proposed. The effect of Ni-CFA on the corrosion resistance of ZRCs was investigated systematically using open-circuit potential (OCP) measurements, the DC polarization technique and electrochemical impedance spectroscopy (EIS). The results showed that the addition of 6.6 wt% Ni-CFA noticeably improved the cathodic protection of the coating due to the electrical conductivity of the Ni layer and decreased the corrosion current when providing barrier protection. Meanwhile, the active SiO2 on the surface of CFA was found to increase the degree of cross-linking of the potassium silicate, resulting in better mechanical properties of the coating, as measured using a bending test. Three corrosion stages were observed, with equivalent circuits expressed by R(QR), R(Q(R(QR)))(QR) and R(Q(RW)).