光老化对丙烯酸聚氨酯/钢板界面附着力的影响

Effect of photo degradation on the adhesion at acrylic polyurethane varnish/steel interface

为了研究光老化对涂层/钢板界面附着力的影响,利用室外(拉萨、武汉)大气曝晒试验与室内人工老化加速试验装置对丙烯酸聚氨酯涂层钢板进行了老化试验。采用拉拔法和电化学交流阻抗技术(EIS)分别评价了老化前后涂层/钢板界面的干附着力和湿附着力性能。拉拔法测试结果表明,涂层的干附着力随老化时间延长而减小。基于EIS电化学参数得到了与其相似的结果,即失粘面积随老化时间增加而增大。同时发现在相同试验周期内荧光紫外老化加速试验比氙灯加速老化试验所产生的涂层失粘面积更大,这与在紫外辐射较强地区(拉萨)和较弱平原地区(武汉)曝晒后所得结果具有很好的对应性,表明增大紫外辐照强度会促进涂层湿附着力降低。研究证实,光老化使涂层附着力减小,从而加速涂层下钢板腐蚀的发生和发展。

To study the effect of photo degradation on the adhesion at coating/steel interface,the acrylic polyurethane varnish（APV） coatings on the steel were aged under outdoor field environments in the cities of Wuhan and Lhasa and the indoor artificial weathering environments.Pull-off adhesion measurement and electrochemical impedance spectroscopy were applied to investigate the adhesion of dry coating and the wet adhesion at coating/steel interface,respectively.It is found from pull-off measurements that the adhesion decreases with aging time increasing.The same trend is observed in the change of coating delamination area,which is deduced from EIS parameters.That is,the delamination area enlarges with aging time.Based on EIS results,it is found that the delamination area produced by fluorescent UV/condensation weathering device is larger than that by xenon lamp exposure and weathering equipment.This result is also verified by comparing the samples respectively exposed in Lhasa with higher irradiation intensity and Wuhan with less irradiation intensity,which indicates that the enhancement of UV intensity impairs the wet adhesion of coating.Thus,photo degradation undermines the adhesion at the coating/steel interface and further accelerates the underneath corrosion of coatings.