Corrosion Resistance of Flame Sprayed Pure Zinc and Zn-Al Alloy Coatings

The flame sprayed coatings of pure zinc, Zn-15Al and Zn-30Al alloy were prepared on surface of 6061-T6 aluminum alloy. The micromorphology, neutral salt corrosion resistance and electrochemical properties of the coatings were studied. The results show that the pure zinc, Zn-15Al alloy and Zn-30Al alloy coatings had dense cross section structure and decreasing porosity inturn, and was mechanically combined with the matrix. After neutral salt spray corrosion, the corrosion mass increased and the corrosion rate decreased in turn of pure zinc, Zn-15Al alloy and Zn-30Al alloy coatings, and the Zn-30Al alloy coatings showed the best resistance to neutral salt spray corrosion. In the artificial seawater solution, the open circuit potential of the three kinds of coatings was lower than that of the aluminum alloy substrate, indicating that the coatings could provide sacrificial anodic protection to the substrate. Compared with those of the pure zinc coating, the self-corrosion current density of Zn-15Al alloy and Zn-30Al alloy coating was lower and the self-corrosion potential was higher, namely the corrosion rate was smaller and the corrosion tendency was lower. With the prolongation of immersion corrosion time, the corrosion resistance of Zn-15Al alloy coating had no significant change, and that of Zn-30Al alloy coating gradually increased. The Zn-30Al alloy coating showed the best electrochemical corrosion resistance.