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目的：研究热浸镀彩涂板常用金属镀层（铝锌合金镀层与纯锌镀层）对彩涂板耐蚀性能的影响。方法通过断面金相、SEM及EDS能谱、循环腐蚀试验和电化学阻抗测试(EIS)等方法，全面对比研究相同单面镀层厚度的镀铝锌与镀锌彩涂板的耐蚀性能。结果在长达250个循环（共计2000 h）的腐蚀试验中，镀锌彩涂板出现了严重的红色锈迹，而镀铝锌彩涂板并未出现明显腐蚀。在 EIS 测试中，两种彩涂板最初的阻抗值约为2×109Ω· cm2，浸泡2 d后镀锌彩涂板阻抗值急剧下降至1.165×108Ω· cm2；浸泡前期，镀铝锌彩涂板阻抗值缓慢下降，15 d后从6.979×108Ω·cm2急剧下降至2.984×107Ω·cm2。EIS等效电路拟合参数表明，镀铝锌彩涂板的电荷转移电阻比镀锌彩涂板高，相应的双电层电容低。SEM和EDS测试结果显示，铝锌合金镀层由底层合金层和外层的富铝和富锌的两相结构组成，而纯锌镀层则由底层合金层和外层纯锌层组成。结论铝锌合金镀层具有独特的富铝和富锌两相结构，使得同等镀层厚度的镀铝锌彩涂板比镀锌彩涂板具有更高的耐蚀性能。

ABSTRACT:Objective To investigate the effects of metal coatings (Al-Zn alloy coating and pure zinc coating) on the cor-rosion resistance of prepainted sheets. Methods Metallographic observation, scanning electron microscopy (SEM), energy dis- persive spectrum(EDS), cyclic corrosion test and electrochemical impedance spectroscopy(EIS) were used to analyze and com-pare the corrosion resistance of the two kinds of prepainted sheets which had the same thickness of metal coating.Results In corrosion test of 250 cycles (a total of 2000 h), serious red rust appeared on the prepainted sheets of pure zinc coating, and no obvious corrosion on the surface of Al-Zn alloy coating prepainted sheets. In the EIS test, the initial impedance value of the two kinds of prepainted sheets were both about 2×109Ω·cm2. The impedance value of prepainted sheet of pure zinc coating sharply declined to 1.165×108Ω·cm2after 2 days immersion, while undergoing slowly descending, the impedance value of Al-Zn alloy coating prepainted sheet sharply declined from 6.979×108Ω·cm2to 2.984×107Ω·cm2after 15 days immersion. The equivalent circuit fitting parameters for EIS showed that charge transfer resistance of Al-Zn alloy coating prepainted sheet was one order of magnitude higher than that of Zn coating prepainted sheet, and the corresponding double-layer capacitance was one order of magnitude lower. SEM and EDS tests showed that Al-Zn alloy coating was composed of inner alloy layer and outer two-phase structure which consisted of alumina-rich phase and zinc-rich phase, while Zn coating was composed of inner alloy layer and outer pure zinc layer.Conclusion Prepainted sheet of Al-Zn alloy coating has better corrosion resistance than that of pure zinc coating due to the unique two-phase structure of Al-rich and Zn-rich.