Corrosion behavior of arc sprayed Al-Zn-Si-RE coatings on mild steel in 3.5 wt% NaCl solution
详细信息 查看全文
- 作者：Qiong Jiang ; Qiang Miao ; Wen-ping Liang ; Feng Ying ; Fei Tong ; Yi Xu ; Bei-lei Ren ; Zheng-jun Yao ; Ping-ze Zhang
- 关键词：Al&ndash ; Zn&ndash ; Si&ndash ; RE coating ; Corrosion morphology ; Corrosion behavior ; Electrochemical impedance spectroscopy ; Protective mechanism
- 刊名：Electrochimica Acta
- 出版年：1 January, 2014
- 年：2014
- 卷：115
- 期：Complete
- 页码：644-656
- 全文大小：4039 K
文摘
Al-Zn-Si-RE coating was deposited on mild steel by arc spraying Al-Zn based alloy wire with a high Al content. The corrosion behavior of Al-Zn-Si-RE coating was investigated by corrosion morphologies and electrochemical measurements. The results indicated that Al-Zn-Si-RE coating exhibited homogeneous distributions of elements and a dense homogeneous lamellar microstructure with good scale adhesion. The phases of the coatings are Zn-rich phase, Al-rich phase, Al0.403Zn0.597 and Al9Si phase. Corrosion products had been deposited in the defects, which caused self-sealing behavior and hindered further corrosion. Corrosion products formed on Al-Zn-Si-RE coating surface consisted mainly of simonkolleite [Zn5(OH)8Cl2路H2O], zinc aluminum hydrotalcites [Zn0.71Al0.29(OH)2(CO3)0.145路xH2O, Zn0.70Al0.30(OH)2(CO3)0.15路xH2O, Zn6Al2(OH)16CO3路4H2O] and aluminum chloride hydroxide hydrate [Al5Cl3(OH)12路4H2O]. Corrosion products had been deposited in the defects, which caused self-sealing behavior and hindered further corrosion. Furthermore, sacrificial anodic protection played a dominant role during the corrosion process. There were different corrosion stages of the coating in sodium chloride solution, such as pitting-dissolution-redeposition, active dissolution, cathodic protection and physical barriers caused by corrosion products. Finally, schematic model of the protective mechanisms of Al-Zn-Si-RE coating during immersion in sodium chloride solution was given.