鋁箔在含銅、鉀離子鹽酸中之三角波交流電蝕

Electrochemical Etch of Al-foil by AC-triangular Wave in Hydrochloric Acid Containing Cu2+ and K+ Ions

本研究在探討商業純鋁（99.98%）箔片在含微量（0 ~ 70 ppm）銅或鉀離子之6N鹽酸溶液中，施加三角波交流電會有不同的蝕刻行為。定電流循環極化法（GVP）所得圖譜顯示：鹽酸中若含銅離子，則其破裂電位（Eb）隨銅離子濃度上升而下降；反之，Eb隨鉀離子濃度增加而上升。鋁箔經蝕刻後，在掃瞄式電子顯微鏡與原子力顯微鏡觀察下所得之形貌顯示：鋁箔表面之孔蝕因銅離子存在而加劇；而因鉀離子存在而減緩。利用化學分析電子術（ESCA）解析鋁箔表面化合物成分得知：在鹽酸中添加銅離子，會有銅還原析出於鋁箔表面，導致伽凡尼腐蝕而使其破裂電位（Eb）與破裂阻抗（Rb）下降，濃度愈高，影響愈大，表面氧化膜更易破裂，造成鋁箔嚴重孔蝕。反之，隨鉀離子濃度之增加，其破裂電壓（Eb）與破裂阻抗（Rb）上升，氧化膜更加穩定，因而鋁箔表面不易孔蝕。

Electrochemical etch of aluminum foil in commercial pure grade (99.98% in purity) in 6 N HCl employed with an ac-triangular galvanostatic voltammetry polarization(GVP) was investigated. Addition of trace amounts (0 ~ 70 ppm) of copper and potassium salts in the electrolyte resulted in different etching behaviors. The characteristic anodic peak (i.e., Eb, the breakdown potential of the anodic film) on the GVP curves is lowered in the presence of copper ion but is heightened in the presence of potassium ion. The higher concentration of these cations the greater is their effect. The morphology examined through scanning electron microscopy and atomic force microscopy revealed that aluminum pitting is magnified by copper ion but diminished by potassium ion. ESCA analysis exhibited that metallic deposition of copper on the Al-foil results in galvanic corrosion so that magnifies pitting corrosion. On the contrary, addition of potassium results in stabilization of oxide film thus diminishing the pitting.