Electrochemical properties of aluminum tripolyphosphate modified chemically bonded phosphate ceramic anticorrosion coating

An inorganic coating, combining chemically bonded phosphate ceramic (CBPC) binder and aluminum tripolyphosphate (ATP) pigment, was designed and prepared for anti-corrosion treatment of steel. An electrochemical method was proposed to characterize and evaluate the corrosive behavior of the coating, and the influence of ATP contents associated with XRD and SEM/EDS techniques. The experimental results showed that the addition of the ATP pigment increased the corrosion potential and reduced the corrosion current density, porosity, and water absorption of a coating. Moreover, the polarization resistance (R-p) values were more than twice those of CBPC binder when the ATP was added. The best anticorrosion profile of the coating was observed when the content of ATP pigment was 15%, which exhibited the least negative corrosion potential (E-corr) and R-p and smallest corrosion current (I-corr). SEM-EDS results indicate that ATP exhibited more metal ion chelating power than the CBPC binder itself, which shows the better interfacial binding ability. The said coating cannot only provide excellent physical protection but form passivation layer on the surface of a steel substrate to protect it and prevent further corrosion. (C) 2020 Elsevier Ltd. All rights reserved.