电弧喷涂铝涂层在海洋环境中的腐蚀机理

Corrosion mechanism of arc spraying aluminum coatings in marine environment

采用电弧喷涂技术在Q235钢基体上制备了铝涂层,并用完整涂层和局部破坏涂层两种试样进行室内模拟浸泡腐蚀实验,腐蚀介质为3·5%NaCl水溶液,流速为0·6m·s-1,实验温度为50±1℃.结果表明:涂层局部破坏时的腐蚀速度与涂层完好时相差不大;铝涂层表面的均匀腐蚀并不严重,铝涂层的腐蚀主要是由于闭塞电池和活性-钝性腐蚀微电池的联合作用引起的局部腐蚀,主要类型为点蚀,且涂层层状剥落形成蚀坑;腐蚀介质到达基体时,将发生电偶腐蚀,铝涂层会作为牺牲阳极保护基体免受腐蚀.

Aluminum coatings were sprayed on Q235 steel by arc spraying. The failure process was studied through the simulated immersing tests in 3.5 % NaCl solution at a fluid velocity of 0.6 m·s^-1 and a test temperature of 50 ± 1 ℃. The results showed that there was little difference in the corrosion rates of undamaged and partially damaged samples. Uniform corrosion of the aluminum coatings was slight. Local corrosion occurred on the coatings because of synergism of the occluded cell and the active-passive cell. The main corrosion type was pit corrosion which induced bed separation and pits. Once corrosive solution arrived at the substrate, galvanic corrosion occurred, and aluminum coatings acted as the sacrificial anode protecting the steel substrate from corrosion.