目的 研究5A06型铝基材所使用的锌黄环氧底漆/丙烯酸聚氨酯面漆涂层体系的失效过程。方法 设计“紫外/冷凝3 d+中性盐雾3 d+低温暴露1 d”为一个周期的实验室循环加速试验，采用交流阻抗谱法，结合光泽度、色差值、红外光谱等数据，研究涂层体系性能。结果 循环加速试验进行到16周，该过程中面漆的失光率、色差值上升，达到轻微失光等级和轻微变色等级。面漆的表面形貌及涂层的低频阻抗发生明显变化，第12周时在光学显微镜下明显可见微小鼓泡，涂层0.1 Hz阻抗保持在109 ??cm2以上，但此后鼓泡数量增加，部分鼓泡破损，颜填料流出；第14周时，0.1 Hz阻抗下降到108 ??cm2，此后鼓泡数量进一步增加，部分鼓泡处面漆脱落；第16周时，0.1 Hz阻抗下降到约为107 ??cm2。结论 丙烯酸聚氨酯面漆树脂基体特征官能团、聚合物链发生断裂，面漆的完整性遭到破坏，这可能与紫外线照射相关。这将加速涂层中腐蚀性介质（如水、氧和侵蚀性氯离子）渗透，促进涂层的失效。

The work aims to study the failure process of a composite coating system composed of zinc yellow epoxy primer and acrylic polyurethane topcoat used in 5A06 aluminum substrate. The laboratory cyclic accelerated test with a cycle of “UV/condensation for 3 days, neutral salt spray for 3 days and low temperature exposure for 1 day” was designed. The performance of the composite coating was studied by adopting AC impedance spectroscopy and measuring gloss, color difference and IR. At 16 cycles of the cyclic accelerated test, the gloss loss and color difference of the topcoat increased to the level of slight loss of gloss and slight discoloration. The surface morphology of the topcoat and the impedance module changed obviously. At 12 cycles, small blister was observed obviously in the optical microscope, but the impedance module at 0.01 Hz of the coating remained above 109 ??cm2. From 12th cycles, the number of blisters increased and some of broken blisters caused the out flowing of pigment. At 14 cycles, the impedance module at 0.01 Hz lowered to 108 ??cm2. The blisters continuously increased and part of them peeled off. At 16 cycles, the impedance at 0.01 Hz lowered to 107 ??cm2. The breakage of characteristic functional groups and polymer chains of the resin matrix of acrylic polyurethane topcoat, and incompleteness of the coating may be caused by UV irradiation and accelerate the permeation of the corrosive medium such as water, oxygen and corrosive chloride, thus resulting in coating failure.