CORROSION RESISTANCE OF ELECTROPLATED Zn-Al COMPOSITE COATING

The corrosion resistance of plain Zn and Zn-Al composite coating was comparatively investigated through corrosion immersion,electrochemical polarization curves,AC impedance and X-ray diffraction.Zn-Al composite coating exhibits better corrosion resistance in 5%NaCl and 10%HCl solution than plain Zn coating.Polarization curve and AC impedance measurements indicated that Zn-Al composite coating showed lower corrosion current,increased polarization resistance and electrochemical impedance,and reduced corrosion rate than plain Zn coating.The composite coating presented preferred orientation on (002),which is probably the reason for increase in its corrosion resistance.