Improvement of Corrosion Resistances of Organosilane-Epoxy Coating on Al Alloy 6101 with Addition of Zinc Phosphate Pigment

The organosilane-epoxy coating material is used for metal protection against corrosion as it has strong adhesion property on a metal substrate due to its multi coordinate sites. In the present paper, the corrosion resistance of organosilane-epoxy coating was improved by the addition of a zinc phosphate pigment. As compared to the pure organosilane-epoxy coating on Al alloy 6101, the mechanical property and electrochemical impedance spectroscopy studies on the organosilane-epoxy coating with addition of a zinc phosphate pigment at a concentration 0.6 wt % show that the modified coatings on Al alloy 6101 have stronger peeling off force than the pure coating on Al alloy 6101, which is increased by 55%. The corrosion protection efficiency of the zinc phosphate pigment modified coating is enhanced by at least 98% comprehensively, in an alkaline solution of NaOH with pH 11, via all tests including mass loss, potentiodynamic polarization, and electrochemical impedance spectroscopy. Scanning electron microscope and X-ray energy dispersive spectroscopy mapping show a good dispersed distribution of the zinc pigment in the coating.