高静水压力对水在环氧涂层中传输行为的影响

EFFECT OF HIGH HYDROSTATIC PRESSURE ON DIFFUSING BEHAVIOR OF WATER THROUGH EPOXY COATING

利用传统增重法和电化学阻抗测量技术研究了常压和深海高静水压力条件下水在环氧涂层中的传输行为。计算出了不同环境下水的扩散系数,并分析了静水压力对水在涂层中吸水动力学的影响。结果表明,高静水压力加速了水在涂层中的传输过程,使其扩散机制由常压下的理想Fick扩散行为变为S吸收型的非理想Fick扩散行为;扩散动力学参数,包括扩散速度、饱和时间和饱和吸水率均发生了明显变化;与涂层阻滞性能密切相关的涂层电容、涂层电阻和特征频率等参数随浸泡时间的变化在高压下也更为显著,涂层提前发生失效。

The diffusing behavior of water through epoxy coating under ordinary pressure （1 atm） and high hydrostatic pressures in deep ocean （35 atm） was investigated by traditional gravimetric method and electrochemical impedance spectroscopy （EIS）. The corresponding diffusion coefficients were calculated and the effect of hydrostatic pressures on kinetics of water adsorption was also analyzed. The results showed that high hydrostatic pressure accelerated the diffusion process of water through organic coating, and the diffusion mechanism had been changed from ideal Fick diffusion under latm to S type adsorption non-ideal Fick diffusion under 35 atm. The parameters for diffusion kinetics, including diffusion velocity, saturation time and saturated percent of water adsorption were significantly different under two environments. The changes of parameters relevant to the barrier property of epoxy coating with immersion time were also severer under high pressure, including the coating capacitance Cc, coating resistance Rc, and break-point frequency fb, resulting in coating failure before its lifetime.