LY12铝合金阳极氧化膜受热后的开裂及其对腐蚀电化学行为的影响

Effect of Cracking on Corrosion Behavior of Anodic Films of LY12 Aluminum Alloy After Heating

用扫描电子显微镜和电化学方法研究了LY12合金阳极氧化膜受热开裂行为和开裂前后的电化学行为。LY12铝合金阳极氧化膜经沸水封闭后存在网络状非穿透性微裂纹;加热后,裂纹在热应力作用下拓宽并发展成穿透性裂纹。引入了裂纹密度(单位面积上的裂纹总长度)和开裂部分所占的面积比来定量表征氧化膜的开裂程度。氧化膜受热开裂以后,其保护性能显著降低,极化电流增大而阻抗值明显降低;氧化膜耐蚀性的变化与裂纹面积比有关,裂纹面积比增大,阻抗与耐蚀性降低。

The cracking and electrochemical behaviors of anodic film of LY12 alloy after being heated at 300℃ were investigated by scanning electron microscopy and electrochemical methods. The results show that some micro-cracks were formed in the sealed anodic films of the alloy before being heated. After being heated at 300℃, the crack density kept almost unchanged but the initial micro-cracks became wider and deeper and might penetrate through the film. Partial abruptions occurred on the oxide/metal interface The ratio of cracked part of substrate covered by anodic film to the total area was employed to represent the electrolyte penetration through the barrier layer in attacking the substrate. The cracking of films resulted in a decrease of the film resistance and an increase of the corrosion current density. Corrosion resistance of the film was related to the ratio of cracked area to the total area. The polarization current density was hardly affected by the ratio. But at a relatively high polarization potential, the film resistance was decreased and the corrosion rate was increased as the ratio was increased.