Effect of Mg content on structure and corrosion behavior of novel hot-dip Al-Zn-Si-rE-Mg coatings

摘要

In this work, the effect of Mg content on structure and corrosion behavior of novel hot-dip 55Al-Zn-1.5Si-0.08RE-xMg (wt.%) coatings were investigated. It was found that the addition of Mg element led to the formation of double-layer or even triple-layer dendrites, as well as induced the generation and distribution of MgZn2 and Mg2Si phases. In addition, Mg also promoted the conversion of corrosion product film from porous AlO(OH) to dense Zn6Al2(OH)16CO(3).4H(2)O (Zn-Al LDH), and retarded the corrosion of Al-rich dendrites. When Mg content was 1.0 wt%, the coating had the smallest dendrite structure, the most protective corrosion product film and the best corrosion resistance with corrosion current density of 2.7 mu A/cm2 and charge transfer resistance of 31550 omega.cm(2).