无溶剂环氧防腐涂层在模拟海水冲刷条件下的电化学行为

Electrochemical Behavior of Solvent-free Epoxy Coating during Erosion in Simulated Flowing Sea Water

通过EIS对3种无溶剂环氧防腐涂层在60℃下流速为2 m/s、含1%(质量分数)石英砂的模拟海水环境中的失效行为进行了研究,并利用SEM观察了冲刷后涂层的表面形貌,利用激光共聚焦显微镜(CLSM)观察了涂层/金属的断面形貌。结果表明,与静态条件相比,流动含砂条件明显加速了无溶剂涂层的失效过程。冲刷条件下,胺类固化环氧粉末涂层和酚醛胺固化环氧液体涂层由于固化交联速度慢,结构比较致密,失效过程主要分为3个阶段:介质在涂层中传输阶段、基体金属腐蚀发生阶段和基体金属腐蚀发展与涂层失效阶段;酚醛固化环氧粉末涂层由于固化速度快,内部孔隙较多,涂层较快形成贯穿通道,失效中期阶段缩短且不明显,失效过程主要为两个阶段。研究结果表明,涂层体系内部存在孔隙是加速涂层失效的一个重要因素。

The electrochemical behavior of three solvent-free epoxy coatings on Q345E carbon steel during corrosion-erosion induced by flowing slurry of simulated sea water with 1% （mass frac- tion） of sand at 60 ~C was investigated by means of electrochemical impedance spectroscopy （EIS）, scanning electron microscope （SEM） and confocal laser scanning microscopy （CLSM）, respective- ly. The results showed that the flowing slurry induced erosion aggravated the deterioration of coat- ings. The amine-cured epoxy powder coating and phenolic aldehyde amine-cured liquid epoxy coat- ing were cured with slow speed and thus much densified, accordingly, their deterioration process experienced three stages： firstly, the inward migration of corrosive medium; secondly, the corrosion initiation of the substrate metal; thirdly, the corrosion propagation of the substrate metal beneath the coating and finally the failure of coatings. On the contrary, the phenolic aldehyde-cured epoxy powder coating was cured with fast speed and thus much porous, its deterioration process experi- enced two stages with a shortened second stage. Therefore, the existence of pores in the coating is one of the important factors for inducing failure of coatings during corrosion-erosion.