在盐湖地区暴露48个月纯锌的腐蚀行为

采用X射线衍射(XRD)、扫描电子显微镜(SEM)、金相显微镜和电化学阻抗等手段研究了锌在青海盐湖大气环境(富盐干旱型大气环境)中的腐蚀行为。结果表明,在青海盐湖大气环境中锌的腐蚀规律遵循经验公式m=Atn。锌的向地面比向天面腐蚀严重,向天面暴晒48个月出现锈层脱落现象。两个表面的腐蚀产物均由Zn5(OH)8Cl2·H2O,Zn5(CO)3(OH)6和Zn4SO4(OH)6·3H2O组成,锈层均富含SiO2。电化学结果表明,随着暴晒时间的延长向地面的极化电阻Rp逐渐增大,而向天面的Rp逐渐增加,而暴晒48个月时减小。锈层有抑制基体腐蚀的作用,对两个表面锈层的保护性随暴晒时间的延长而增大,而向天面暴晒48个月时保护性减弱。

Corrosion Behavior of Zinc Exposed to Salt Lake Area for 48 Months

Corrosion behavior of zinc was field exposed to salt-rich arid atmosphere at Qinghai salt lake of Qinghai province at the Northwest China for 48 months was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), metalloscopy and EIS techniques.Results reveal that the corrosion kinetics of zinc in the atmosphere at a selected site followed the empirical equation m=Atⁿ. The corrosion of zinc on the skyward surface is heavier than that on the fieldward one, while spallation of the rust layer on the skyward surface did occur after exposure for 48 months. The corrosion products on the two surfaces were mainly composed of Zn₅(OH)₈Cl₂·H₂O, Zn₅(CO)₃(OH)₆, Zn₄SO₄(OH)₆·3H₂O, the rust layer contained also certain amount of SiO₂. The results of EIS analysis showed that the rust layer could suppress the corrosion of zinc substrate, the corrosion resistance of rust layers on the two surfaces increased with time, then the protectiveness of the rust layer on the skyward surface was weakened for 48 months exposure.