高强度钢代镉铝基涂层耐海洋环境腐蚀性能评价

目的评价高强度结构钢300M上电镀镉-钛、离子镀铝、无水电镀铝三种防护涂层的耐海洋环境腐蚀性能。方法采用中性盐雾试验和海洋环境大气暴露试验进行评价,并在试验后观察涂层宏观、微观形貌,分析腐蚀产物成分。结果离子镀铝涂层表面在盐雾试验96 h出现白色的腐蚀产物、336 h出现红色的腐蚀产物;电镀铝在336 h出现白色的腐蚀产物、500 h出现红色的腐蚀产物。电镀镉-钛盐雾试验1000 h没有白色腐蚀产物。离子镀铝涂层和电镀铝涂层海洋环境大气暴露试验0.5 a出现了白色的腐蚀点、1 a暴露试验后出现红色的腐蚀点,且在划叉区域出现了红色的腐蚀产物,而电镀镉-钛5 a户外暴露试验仅在划叉部分出现了少量的红色的腐蚀产物。离子镀铝涂层和电镀铝两种涂层均易发生铝涂层的点蚀,随着腐蚀时间的延长,点蚀深入,发生基体的腐蚀出现红锈。结论离子镀铝、无水电镀铝两种铝基涂层比电镀镉-钛的耐蚀性稍差,镉-钛镀层对基体有良好的牺牲阳极的作用,保护基体免受腐蚀,而铝涂层对基体的保护作用较弱,划叉部位出现红色的腐蚀。

Corrosion Property at Marine Atmosphere of Al Based Coatings Replacing Cd on High Strength Steels

Objective To evaluate the corrosion property at marine atmosphere of three kinds of protective coatings on high strength steels, including electroplating Cd-Ti ( Ed Cd-Ti), ion vapour depositing aluminium (IVD Al) and electroplating Aluminium( Ed Al). Methods Neutral salt fog test, marine atmospheric outdoor exposure test, macroscopic and microscopic observation of the three coatings before and after corrosion tests were carried out to observe macroscopic and microscopic morphology of coating and analyze components of corrosion products. Results White corrosion products on IVD Al and Ed Al coatings appeared after 96h and 336h of test, and red corrosion products appeared after 336h and 500h of test, but there was no corrosion product after 1000h of test on Ed Cd coatings. The marine atmospheric outdoor exposure tests results showed that there were white corrosion pits on IVD Al and Ed Al after half a year test, and red corrosion pits appeared after one year of exposure test, and corrosion occurred to the cross-section after one year of test. While only little corrosion product appeared on cross-section after one year of exposure test on electroplating Cd-Ti. Both the two coatings were likely to suffer from corrosive pitting on aluminized coating. The corrosive pitting went deeper as time went by. Red rust appeared on the matrix of corrosion. Conclusion The anti-corrosion property of IVD Al and Ed Al are inferior to that of Ed Cd. Cd coating can provide anodic sacrificed effect on the steel substrate while the IVD Al and Ed Al has less sacrificed effect.