Effect of ZnAl-LDH on corrosion resistance of Zn-55Al alloy in NaCl solution

ZnAl layered double hydroxides (Zn6Al2(OH)(16)CO3, LDH) are the unique phase in the corrosion products of Zn-Al coating compared with the corrosion products of pure Zn coating. The effect of LDH on the corrosion resistance of Zn-55Al coating is investigated in this work. The LDH preferentially grows on the Zn-rich region of Zn-55Al alloy, and then gradually grows on the Al-rich region. The prepared LDH film can effectively inhibit the formation of simonkolleite (Zn-5(OH)(8)Cl-2, ZHC), hydrozincite (Zn-5(CO3)(2)(OH)(6), HZ), and ZnO in the corrosion product film of Zn-55Al alloy, making the corrosion product film more dense and less prone to cracking, which can effectively prevent the corrosion of Zn-55Al alloy. The LDH film can effectively reduce the corrosion current density and improve the electrochemical impedance of pure Zn. In the end, the corrosion protection mechanism of LDH on the surface of Zn-55Al alloy was discussed.