壓鑄AZ91D鎂合金在3.5wt % NaCl水溶液中之腐蝕行為

The Corrosion Behavior of Die-Cast AZ91D Magnesium Alloy in 3.5 wt NaCl Solution

本研究主要探討壓鑄AZ91D鎂合金在3.5 wt%NaCl水溶液中，不同pH值下之電化學反應與腐蝕行為。此壓鑄鎂合金含有固溶相（α）及Mg17Al12介金屬化合物（β）。在中性NaCl水溶液中，其腐蝕損失量與時間呈線性關係。由SEM觀察試片表面腐蝕型態與XRD 分析腐蝕產物得知AZ91D中α相與β相之間的電位差會使得腐蝕容易在鄰近β相的α相發生，且造成β相的脫落。開路電位及極化曲線的數據顯示在鹼性的氯化鈉水溶液環境中AZ91D鎂合金表面能生成較穩定的Mg(OH)2而有鈍化的現象。

The electrochemical and corrosion behaviors of die-cast AZ91D alloy in 3.5 wt NaCl solution with different pH were investigated. This die-cast magnesium alloy exhibited a solid solution phase (α) and an intermetallic compound Mg17Al12 ( ). In neutral NaCl solution, the weight loss due to corrosion was found to vary linearly with time. The results of SEM surface morphology and XRD of corrosion product revealed that the potential different between phase and β phase in AZ91D alloy would make the corrosion localized in α phase adjacent to α β phase and cause the drop of β phase. In alkaline solution, the results for both open circuit potential and polarization measurements indicated that AZ91D alloy could be passivated due to the formation of a relative stable Mg(OH)2 film.