Cr元素對Al-Mg合金陽極與耐蝕性質之研究

The Effect of Cr Element on the Anodic oxidation film and Corrosion Behavior of Al-Mg alloy

Al-Mg鋁合金因質輕、高強度與色澤美觀等特性，已成為可攜式3C/IT產品殼件之首選。而不同元素添加比例會影響其合金電化學特性，本研究利用電化學陽極處理、動電位極化曲線法和交流阻抗頻譜，探討不同Cr含量對Al-Mg合金陽極處理後陽極膜性質之影響以及其素材在硫酸或NaCl溶液中的電化學行為和耐腐蝕性質，並利用電子顯微鏡進行微觀分析。研究結果顯示，Cr含量增加會使Al-Mg合金之陽極後色差b*值增加，使陽極膜偏向暗黃色澤；電化學腐蝕測試結果顯示，增加Cr含量會提高Al-Mg合金之腐蝕電位並降低其腐蝕電流值，進而提升Al-Mg鋁合金之耐蝕性。於NaCl溶液中，提高Cl-濃度會促進點蝕的形成與發展，而增加Cr元素含量則可對Al-Mg合金形成較佳之Cl-保護作用。

Al-Mg alloys were anodized in a sulfuric acid solution, and the influence of Cr content on color of anodized films was analyzed. Furthermore, measurements of potentiodynamic polarization curves (PDS), electrochemical impendence spectroscopy (EIS) and scanning electron microscopy (SEM) were utilized to investigate the effects of Cr addition on the corrosion and electrochemical behavior of Al-Mg alloy in H2SO4 or NaCl aqueous solution. The anodic oxidation results show that with Cr addition, the microstructure of anodized film is changed and the b*-value of film increases. The corrosion results show that with Mg addition, corrosion resistance increases with corrosion potential shifting to the positive region and corrosion current density decreasing, and polarization resistance increasing. In the chloride solution, the increase of Cl- concentration could promote the formation and propagation of pitting, and thus the electrochemical behavior of Al-Mg alloy was affected.