干湿交替对有机涂层在模拟海洋工业大气溶液中失效行为的影响

Influence of Wet-Dry Cycles on the Failure of Organic Coatings in Simulated Coastal-Industrial Atmospheric Solution

采用电化学交流阻抗(EIS)、红外光谱(FT-IR)和扫描电镜(SEM)等方法研究了环氧富锌/丙烯酸聚氨酯涂层在模拟海洋工业大气溶液[0.05%NaCl+0.35%(NH4)2SO4]中的失效过程,对比分析了不同干湿循环周期(浸泡8 h-干燥4 h、浸泡4 h-干燥4 h、浸泡8 h-干燥16 h)对涂层劣化行为的影响。结果表明:不同的干湿频率导致涂层吸水以及溶胀/收缩的程度不同。干湿交替8-4周期和4-4周期条件下涂层的低频阻抗值(|Z|0.01 Hz)下降较快,涂层孔隙率与吸水率增长快,聚氨酯面漆水解程度较大,底漆中锌粉反应程度高。干湿8-16周期与全浸试样的低频阻抗值下降较慢,且在后期较接近,吸水率和孔隙率增长最慢。

The degradation of epoxy zinc-rich/acrylic polyurethane coatings system in a simulated coastal-industrial atmospheric solution[0.05%NaCl+0.35%(NH4)2SO4]was studied by using electrochemical impedance spectroscopy(EIS),fourier transform infrared spectroscopy(FT-IR)and scanning electron microscopy(SEM)methods.The effects of different wet-dry cycle conditions[8 h immersion and 4 h dry(8-4 cycle),4 h immersion and 4 h dry(4-4 cycle),8 h immersion and 16 h dry(8-14 cycle)]on the failure of the coatings system were comparatively analyzed.The results showed that,the water absorption of the coatings and the extent of swelling/shrinking were different under various wet-dry cycle conditions.The impedance at low frequency(|Z|0.01 Hz)of the coatings under 8-4 and 4-4 wetdry cycles decreased relatively quickly,the porosity and water absorption of the coatings increased fast,the polyurethane topcoat experienced obvious hydrolytic degradation and the zinc powder in the epoxy primer was corroded to a relatively high extent.The impedance(|Z|0.01 Hz)of the coatings under 8-16 cycle and full immersion condition decreased relatively slowly and approaching similar values at late test stage,accompanied by the slow increase of the coatings porosity and water absorption.