The effect of surface modification of zinc particles with phosphoric acid on the corrosion resistance of cold galvanizing coatings

The surface modification of zinc particles using phosphoric acid was conducted to improve the corrosion resistance of Cold galvanizing coatings. The modified zinc particles were characterized by Scanning Electron Microscope (SEM) and X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS) and Scanning Vibrating Electrode Technique (SVET) were performed to investigate the corrosion protection mechanism of the coating. The electrochemical activity of zinc particles were found decreased because of the formation of Zn-3(PO4)center dot 4H(2)O on the surface of the particle. Little lamellar-shaped phosphate was also observed after surface modification. The best anti-corrosion performance of the coating was achieved when using zinc particles modified with 1% phosphoric acid as the fillings. This improvement was accomplished by the combined effect of reduced electrochemical activity of surface modified zinc particles and block effect from lamellar-shaped phosphate.