模拟流动海水条件下无溶剂环氧防腐涂层的失效行为

Failure Behavior of Solvent-free Epoxy Coating in Simulated Flowing Sea Water

在60℃实验条件下以3种无溶剂环氧防腐涂层为研究对象,利用称重法研究了在不同流速3.5%NaCl溶液中水在涂层中的扩散行为,采用开路电位法(OCP)和电化学阻抗谱技术(EIS)研究了不同流速下涂层的失效行为。结果表明,胺类固化粉末涂层和酚醛固化粉末涂层在实验流速范围内、酚醛胺固化液体涂层在较低流速范围内,水在涂层中的扩散符合Fick II模型,而酚醛胺固化液体涂层在4 m/s高流速下水在涂层中的扩散偏离Fick II模型;随着流体流速增加,涂层的饱和吸水量增加,水在涂层中的扩散系数变大;实验流速范围内3种无溶剂涂层失效过程分为3个阶段;流体流速明显加速了酚醛固化粉末涂层和酚醛胺固化液体涂层的劣化,对胺类固化粉末涂层失效影响不明显。

Three kind of solvent- free epoxy coatings was prepared on 16Mn（Q345E） steel and then their degradation process in flowing artificial sea water 3.5% Na Cl solution was investigated by means of gravimetric method, and the acquired weight gain curves were fitted by Fick model.The effect of the flow velocities on the degradation process of coatings was also studied by open circuit potential method（OCP） and electrochemical impedance spectroscopy（EIS）. The results showed that, for the amine- cured epoxy powder coating and the phenolic aldehyde- cured epoxy powder coating within the scope of the test flow velocities and the phenolic aldehyde amine-cured liquid epoxy coating at lower flow velocities, the diffusion of water through the coatings by different flow velocities all agreed well with Fick II diffusion model. However, the phenolic aldehyde amine- cured liquid epoxy coating showed irregular regulation by flow velocity 4 m/s, which may be due to aggravated dissolution, thus the diffusion of water through the coating departed from Fick II diffusion model. As the flow velocity increased, the amount of saturated water uptake of the coatings and the water diffusion coefficient increased simultaneously. The degradation processes of the above mentioned three coatings within the scope of test flow velocities may be differentiated as a process of three stages. The increase of flow velocity could accelerate the degradation of the phe-nolic aldehyde- cured epoxy powder coating and the phenolic aldehyde amine- cured liquid epoxy coating, but had little influence on the amine-cured epoxy powder coating.