用Kelvin探头技术研究铝合金的大气腐蚀

选择航空工业广泛使用的铝、铝合金及其涂层的试样，利用自行研制的Kelvin探头大气腐蚀测定仪、扫描电镜等设备，研究了纯铝试样随温、湿度变化，其表面电位的变化规律，测定了铝合金及涂层试样大气曝晒试验和周浸试验前后的表面电位、形貌,对铝、铝合金以及涂层的腐蚀规律进行了初步的探讨.结果表明，纯铝试样表面无可见液膜时，腐蚀电位随相对湿度增加逐渐下降；表面有可见液膜时，随着液层蒸发逐渐减薄，电位逐渐正移.铝合金裸材在北京大气环境下电位变化较小，且各个位置的电位基本相同.带涂层的试样优先在缺陷处发生腐蚀，并不断向周围扩展，涂层的剥离面积不断增大.涂层的铝合金，划痕处在腐蚀发生的初期腐蚀电位向负方向变化很快，但是随着时间的延长，腐蚀电位变化的速率减慢，并有向正方向移动的趋势. 

STUDY ON ATMOSPHERIC CORROSION OF ALUMINUM ALLOY BY Kelvin PROBE TECHNIQUE

Atmospheric corrosion of aluminum, aluminum alloy TB04 without and with coatings used widely in aviation industry was investigated in this paper. The variation of surface potential versus ambine temperature and relative humidity for pure aluminum, and the surface potential distribution of 7B04 aluminum alloy without and with coatings before and after the atmospheric exposure for certain period, as well as those after cycleic dry-wet accelerated test exposure were studied using homemade Kelvin Probe atmospheric corrosion test device. The surface morphology of the corroded surfaces was observed by SEM. It shows that the corrosion potential of aluminum samples decreases with the increasing of humidity when there was not visual water film on the its surface. The corrosion potential increases with the decreasing of thickness of visual water film. The potential of naked 7B04 exposed in Beijing atmospheric environment did not change much and it was almost the same on the whole surface. Coated samples of TB04 alloy are first corroded on the sits with defect, and then the coating are delaminated in the initial period of corrosion, the potential on the sit with defect will drop to more negative value and change greatly, but the change rate will decrease and there is a tendency that the corrosion potential shifted towords positive with time.