析出物粒子對陽極處理鋁合金之耐蝕性影響

Effect of Precipitate Particles on Corrosion Resistance of Anodized Al Alloy

本研究探討經不同熱處理所得AA6061鋁合金之析出物粒子對其陽極氧化膜的成膜及耐蝕性影響。將AA6061鋁合金試片置入530℃持溫1小時後，施以爐冷及水淬不同冷卻方式，部份淬冷試片再經8小時之時效處理，獲得不同析出物顆粒型態，最後試片再進行陽極處理。以光學顯微鏡及電子微探儀觀察陽極氧化膜的成膜微觀組織變化，以及進行3.5wt%氯化鈉水溶液及1.0 wt%次氯酸鈉水溶液之極化曲線實驗評估腐蝕行為。研究結果顯示，AA6061鋁合金生成析出物粒子有Al-Fe-Si雜質相及Mg2Si強化相。當兩種析出相過大，會影響陽極氧化膜的緻密性；若Al-Fe-Si析出相尺寸大於陽極氧化膜厚度一半以上，將會產生陽極氧化膜破孔而影響緻密性。極化曲線之數據顯示，若陽極氧化膜的緻密性越好，則所得腐蝕電流密度越低，耐腐蝕性越佳，反之亦然。

The effect of the second phase particles of AA 6061 aluminum alloy on the formation of anodized film and corrosion resistance of anodized Al alloy has been investigated. AA6061 aluminum alloy specimens were soaked into salt bath at 530 ℃ for one hour, and then cooled in different ways (furnace cooling and water quenching). The quenched specimens were further aged in 180 ℃ oil bath for 8 hours. After the anodizing treatment of the heat treated Al specimens had been finished, the microstructure of anodic film were observed by optical microscope and electron probe micro-analyzer. Polarization experiments of anodized specimen in 3.5 wt% NaCl solution and 1.0 wt% NaClO solution were conducted. The results show that there are two precipitate particles such as Al-Fe-Si constituent phase and Mg2Si strengthening phase. If precipitate sizes are larger than the half thickness of the anodized film, some pores were observed at anodized film. The pore channel existed at anodized film decreased the corrosion resistance of the anodized alloy. When the anodic film was dense and thick, the corrosion current density of anodized alloy is lower than those of AA6061 alloy.