环氧铝粉涂层在3.5%NaCl介质中的失效机理研究

采用电化学阻抗谱技术（EIS）研究了环氧铝粉涂层/Q235钢基体在3.5 %NaCl介质中的电化学腐蚀行为.利用扫描电镜（SEM）分析了涂层表面形貌,对涂层断面进行了能谱（EDX）线扫描和界面处腐蚀产物成分分析,探讨了环氧铝粉涂层的腐蚀失效机理.结果表明,腐蚀介质能通过涂层迅速渗透到涂层/基体界面,引起涂层电阻值的降低及界面处电化学腐蚀的开始.失效前涂层致密、连续,失效后涂层表面出现鼓泡、孔洞等现象.鼓泡是由腐蚀产物的体积膨胀和腐蚀介质渗入产生的压力推动共同产生的.界面处腐蚀产物主要是Fe和Al的氧化物及氯化物.涂层的失效机理为腐蚀介质渗入,涂层鼓泡、剥离.

Study on Failure Mechanism of Epoxy Aluminum Coating Immersed in 3.5% NaCl

Electrochemical corrosion behavior of epoxy aluminum coating immersed in 3.5 %NaCl solution was investigated using electrochemical impedance spectroscopy(EIS). SEM and EDX were also used to analyze the surface and cross section images of coating, and the failure mechanism of coating was discussed as well. The experimental results showed that corrosive species can penetrate into coatings and reach the coating/substrate interface promptly, causing the decrease of electro-resistance and the beginning of electrochemical corrosion at the coatings/metal interface. The coating was compact and continuous, while the blisters and cavities occured after corrosion. Blisters were formed by volume expansion of corrosion products, which are mainly oxides and chlorides of Fe and Al, and osmotic pressure created by corrosion species penetration.