AZ91D鎂合金之腐蝕與其陽極膜耐蝕性質之研究

Corrosion Behavior of Anodized AZ91D Magnesium Alloy

本研究探討AZ91D鎂合金經過陽極化處理前後之耐蝕性質變化。利用浸泡實驗以及動電位極化曲線測試探討未經過陽極化處理之AZ91D鎂合金在3.5 wt % NaCl（不同pH值）水溶液中之電化學反應與腐蝕行為。實驗結果顯示在酸性的環境下（pH = 2.0），AZ91D鎂合金所含有之基地（α）及析出相（β，Mg17Al12介金屬化合物）的腐蝕程度相近；而在中性以及鹼性的環境中（pH = 6. 1, pH = 12.0）β相比α相具有較佳的耐蝕性，主要與β相有較高之Al含量有關。而經陽極化處理之AZ91D鎂合金，浸泡於酸性氯化鈉水溶液中，陽極膜會發生溶解的現象，而在中性以及鹼性中，陽極膜則有良好的穩定性。

The corrosion behavior of AZ91D magnesium alloy with or without anodization was investigated. For the non-anodized alloy, both immersion and potentiodynamic polarization tests conducted in 3.5 wt% NaCl solution were employed for corrosion resistance evaluation. In acidic solution ( pH = 2 ), the results revealed that both the matrix phase (α) and the precipitate (β, Mg17Al12, intermetallic compound ) were severely corroded. However, in neutral and in alkaline solutions, β phase had a higher resistance to corrosion than α phase. The better corrosion resistance of β phase was attributed to its high Al content. The anodized film formed on AZ91D magnesium alloy might be dissolved in acidic solution. In neutral and alkaline solutions, however, the anodized films were rather stable.