鋁在酸性溶液中孔蝕行為研究

Pitting Behavior of Aluminum in Acid Solution

本研究主要是探討高純度鋁箔（99.95%），在鹽酸（HCl）溶液中，進行交流電（三角波）蝕刻的孔蝕行為。在電化學特性分析上，將利用定電流循環極化法（GVP），輸入三角波變化電流，以參考電極（SCE）量測試片表面的電壓變化，得到電壓對電流（V-I）變化曲線圖，從曲線變化來推測金屬與溶液界面的電化學反應。並利用掃瞄式電子顯微鏡（SEM），觀察電化學蝕刻後的表面形貌。從改變各種參數的實驗結果發現：增加交流電頻率，會使破裂電壓（Eb）上升（由0.093 V 上升至0.32 V），蝕孔（pit）尺寸變小，形狀從方形孔變為不規則狀，並造成表面局部性蝕刻。蝕刻液中若添加硫酸（H2SO4），陽極半反應有二次鈍化產生，在交流高頻蝕刻時，出現巨大蝕孔（pores）。若蝕刻液中添加氯化鋁，則交流高頻蝕刻的局部腐蝕更嚴重，但不影響交流低頻電蝕之形貌。

Pitting behavior of pure aluminum foils (99.95%) in hydrochloric solution performed at constant alternating current was investigated. A diagram of V-I diagram was plotted from the galvanodynamic voltammetry polarization (GVP) of the aluminum foil in the acid solution. Corrosion morphology of the aluminum foil was examined through scanning electron microscope (SEM). The relationship between the corrosion morphology and the corresponding profile of V-I diagram for the aluminum foil was of interest. Morphology examination revealed that the size of pits and the portion of pitting area decrease markedly with increasing the frequency of the alternating current. Analyzing in the V-I diagram, we found that the breakdown potential(Eb)with its corresponding current density decreases with increasing the ac frequency. The effect of additives indicated that an addition of sulfuric acid in the electrolyte results to intensify the size difference of pits, thus size distribution becoming less homogeneous. The addition of aluminum chloride (AlCl3) in the electrolyte only intensified the pitting corrosion when high frequency ac ( >60 Hz) was applied.