鋁合金對乾蝕刻之耐腐蝕研究

Investigation on the Corrosion Resistance of Anodically Oxidized Aluminum to CF4

本研究以6061鋁合金經由前處理後，再進行陽極氧化處理，鋁合金表面充滿著孔洞，為了提高耐腐蝕，經由沸水封孔處理獲得緻密結構皮膜，防止鋁合金腐蝕，同時增加鋁合金表面高電阻率。鋁合金前處理包含珠擊（Ra 3.5μm）與表面電解拋光整平後，再進行陽極氧化處理。陽極氧化處理採用硫酸、草酸及磷酸溶液，經表面形貌觀察其硫酸溶液形成孔洞約37 nm、草酸溶液形成孔洞約70 nm，磷酸溶液形成孔洞約230 nm，透過沸水封孔處理，發現硫酸浴形成速度快且沈積氧化鋁緻密結構。隨後，將鋁合金放入電感耦合式電漿（ICP）通入四氟甲烷（CF4）氣體進行腐蝕試驗，使用交直流耐壓測試器檢測材料介電強度值。結果顯示隨蝕刻時間增加其表面層介電強度值隨之降低。鋁合金試片經退火處理及再進行蝕刻，其介電強度值下降更快，其耐腐蝕性更差。

In this study, the pretreated 6061 aluminum alloy underwent anodically oxidized treatment to obtain a porous oxide surface, and then boiling-water treated to turn the surface into a compact coating, which not only can increase the corrosion resistance but also the surface electric resistivity. The pretreatments included shot-peening (Ra 3.5 μm) and surface electrochemical polishing. And sulfuric acid, oxalic acid, and phosphoric acid were employed in the anodically oxidization treatment, respectively. Different pore sizes were obtained on the specimen surface for different acid used, i.e. 37 nm, 70 nm, and 230 nm pores for sulfuric acid, oxalic acid and phosphoric acid. During the boiling-water sealing treatment, the specimen oxidized in sulfuric acid showed the fastest oxidation rate and the surface alumina structure was more compact than its counterparts. Then, the surface treated specimens were tested in the induction coupled plasma (ICP) etching with CF4. Following the ICP corrosion testing, the specimens were examined with DC voltage insulation tester. It was found that the dielectric strengthof the coating decreased with the increase in exposure time to CF4. Moreover, the aluminum alloy specimen if further annealed deteriorated both the dielectric strength and corrosion resistance.