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运用四种加速方法对聚氨酯有机涂层钢板进行老化,并通过涂层的表观性能和电化学特征对比研究了老化方式对涂层失效的影响.紫外老化对涂层光泽的影响最大,老化32 d失光度达85.7%.盐雾实验前期线性极化阻力Rp迅速下降,后期由于盐膜的生成使得Rp保持稳定;氙灯和盐雾混合老化的光泽度和Rp的变化规律都表现为实验前期与光老化相似,后期则与盐雾实验相类似.此外,拟合不同老化方式的电化学交流阻抗谱发现:混合老化前期主要受氙灯影响,与单一氙灯老化的等效电路一致,表现为两个时间常数;后期产生盐膜,出现三个时间常数.
Four accelerating methods were used to age polyurethane organic coated steel sheets, and the effects of aging methods on coating failure were studied by the comparison of the apparent and electrochemical characteristics of the coatings.UV aging had the strongest influence on the gloss of the coatings, aging 32 d lost light reached 85.7% .The Rp of linear polarization resistance dropped rapidly in the early stage of salt spray experiment, and Rp remained stable at the later stage due to the formation of salt film. The changes of gloss and Rp in xenon lamp and salt fog mixed aging showed the same trend Photo-aging experiments were similar to those of salt fog experiments. In addition, fitting electrochemical impedance spectroscopy with different aging methods showed that the pre-mixed aging was mainly affected by xenon lamp, which was consistent with the equivalent circuit of single xenon lamp aging, showing two Time constant; salt film occurs later, there are three time constants.