Tuning of η-phase layer with Zr/Al content to enhance corrosion resistance of zinc coating

Abstract

The present study reports about the tuning of Zr/Al content in the η-layer of galvanized zinc coating. The microstructural tuning of the η-phase lead to improvement of corrosion resistant characteristics. Existence of stable oxidation states i.e. Zr4+ and Al3+ is ensured. Uniform distribution of tuned content of Zr and Al in the grain boundaries is achieved. Uniform and homogeneous distribution of spangles is confirmed. Such microstructure and phase modification in the η-layer lead to achievement of very high corrosion potential with very low current density, viz: −1077.4 mV and 102.3 μA/cm2 respectively. The low corrosion rate (0.0272 mmpy) obtained for the composite zinc coating is ascribed to the synergistic interaction of Zr, Al and Zn within the coating matrix. Rct as high as 337.4 Ω cm2 and Cdl as low as 1.637 × 10−6F are also achieved. The study gives insights into the potential scope of the hot-dip composite coatings for several industrial applications such as corrosion resistance, self-lubrication, thermal barrier coatings etc.