热浸镀Zn-Al-Mg镀层在模拟湿热海洋大气环境中的腐蚀行为研究

目的 为详细研究热浸镀Zn-Al-Mg镀层在模拟湿热海洋大气下的腐蚀行为及作用机理，同时为热浸镀Zn-Al-Mg镀层在湿热海洋大气环境中服役提供数据参考。方法 采用腐蚀失重、XRD、SEM、电化学等测试方法对热浸镀Zn-Al-Mg镀层在模拟湿热海洋大气环境下的腐蚀行为进行研究。结果 腐蚀产物主要由Zn₅(OH)₈Cl₂·H₂O组成，腐蚀一段时间后，发现少量ZnO、Zn₅(OH)₆CO₃，腐蚀产物具有与锌腐蚀类似的层状结构，1 848 h呈“三明治”型，相比于上下两层暗色物质，中层亮色腐蚀产物富集更多的Cl元素。热浸镀Zn-Al-Mg镀层腐蚀速率大体随时间延长呈上升趋势，只在672～840 h腐蚀速率下降，对比镀锌在模拟环境和锌在湿热大气环境中的腐蚀，热浸镀Zn-Al-Mg镀层在模拟湿热海洋大气中表现出较好的耐蚀性。结论热浸镀Zn-Al-Mg镀层在模拟湿热海洋大气下腐蚀产物演变与腐蚀过程中Mg的参与有关。腐蚀672～840h阶段腐蚀速率...

Corrosion Behavior of Hot-dip Zn-Al-Mg Coating Exposed to a Simulated Hot and Humid Marine Atmosphere

The work aims to explore the corrosion behavior and mechanism of hot-dip Zn-Al-Mg coatings in a hot and humid marine atmosphere and provide data references for hot-dip Zn-Al-Mg coatings serving in the hot and humid marine atmosphere. The corrosion behavior of the hot-dip Zn-Al-Mg coating in a simulated hot and humid marine atmosphere was analyzed by corrosion weight loss, X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and other test methods. The results showed that the corrosion product was mainly composed of Zn5(OH)8Cl2.H2O. After a period of corrosion, a small amount of ZnO and Zn5(OH)6CO3 were found. The corrosion product evolution was related to the participation of Mg in the corrosion process. The corrosion product had a lamellar structure, which was like a "sandwich" at 1 848 h. Compared with the upper and lower layers of dark substances, the bright-colored corrosion product in the middle layer had more Cl elements concentration. The corrosion rate of the hot-dip Zn-Al-Mg coating generally increased with time, and only dropped sharply in the stage of 672-840 h. Comparison of galvanized coatings corrosion in a simulated hot and humid marine environment and zinc corrosion in a hot and humid outdoor marine atmospheric environment showed that the hot-dip Zn-Al-Mg coating had high corrosion resistance in the simulated hot and humid marine atmosphere environment. The evolution of corrosion products of the hot dip Zn-Al-Mg coating in a simulated hot and humid Marine atmosphere is related to Mg in the corrosion process. The reason for the decrease of corrosion rate at 672-840 h is related to the decrease of ZnO and the increase of Zn5(OH)8Cl2.H2O in corrosion products. It is predicted that the hot-dip Zn-Al-Mg coating still has high corrosion resistance in the hot and humid harsh marine atmosphere, and it can be given priority as a construction material for hot and humid marine atmosphere environment.