硫酸根對鋁箔交流電蝕孔蝕行為之影響

Effects of Sulfate Anions on Pitting Behavior of Aluminum Foils During AC Etching

在鹽酸溶液中添加硫酸根常用來提昇經交流電蝕陽極鋁箔之靜電容量。本研究在0.8M鹽酸中添加0.005 ~ 0.02M硫酸根，並以三角波對鋁箔進行交流電蝕，以探討硫酸根對鋁箔孔蝕行為的影響。藉由電壓/電流/時間曲線量測電蝕反應之破孔電位、溶蝕時間以及孕核時間，並觀察蝕孔深度、連結情形、腐蝕生成物結構與厚度。在適量添加硫酸根後會減小蝕孔穿蝕深度，使蝕孔細緻均勻，減少表層鋁因未完全電蝕而掉落的機率。藉由這些結果對硫酸根濃度於腐蝕生成物及蝕孔形貌與擴展的影響提出可能機制。

Addition of SO42- to hydrochloric acid (HCl) has been shown to effectively enhance the capacitance of aluminum foils used as the anode of low-voltage capacitors. In this study, the aluminum foils were etched in 0.8 M HCl containing 0.005 ~ 0.02 M SO42- using a triangular AC current. The breakdown potential, dissolution time and incubation time were measured from voltage/current/time curves. Cross-sectional TEM was employed to characterize the coalescence, propagation and depth of the pits, as well as the microstructure and thickness of the etch film. Results show that adding proper amount of SO42- in HCl resulted in fine and uniformly-distributed pits with less penetration depth into the substrate. Accordingly, the loss of aluminum due to undermining of the pits diminished. Finally, possible mechanisms regarding the effect of SO42- in HCl solution on the nucleation, growth, coalescence and propagation of the pits are discussed.