铝合金导电管腐蚀失效原因分析

Analysis of Corrosion and Failure Mechanism of Aluminum Alloy Conductive Tube

用于高压隔离开关的铝合金导电管存在着严重而普遍的腐蚀问题,危及高压隔离开关的正常运行。运用能谱分析、金相分析和电子探针等技术对铝合金导电管的破损原因进行了分析。结果表明,导电管存在着高度定向的纵向显微组织和局部脱溶,Cu,Fe等有害元素的相在晶界处大量连续析出,造成晶界附近出现贫化区,由于导电管的工作环境为近海海洋大气带,其中含有大量的侵蚀性阴离子,众多因素是导电管的腐蚀成因。其腐蚀过程为先在表面发生点蚀,然后发展成晶间腐蚀,在晶间腐蚀和内应力的协同作用下最终开裂形成剥蚀。

With a view to the commonly observed severe corrosion of aluminum alloy conductive tube in high voltage isolator and its potential damage to the normal operation of the isolator, the causes leading to the corrosion and failure of the aluminum alloy conductive tubes were investigated by means of energy dispersive spectroscopy, metallography, and electron probe microscopy. It was found that there existed highly oriented lengthwise microstructure and local detaching-dissolving on the Al alloy conductive tube. The deleterious elements such as Cu and Fe were continuously segregated around the grain boundary, which led to the depletion of anti-corrosion aluminum oxide around the grain boundary area. This together with various corrosive anions in oceanic environment accounted for the corrosion and damage of the Al alloy conductive tube. The corrosion and damage of the Al alloy conductive tube was characterized by early stage pitting on the surface, the successive intergranular corrosion, and the final crack and exfoliation corrosion in the presence of combined intergranular corrosion and internal stress.