2205雙相不銹鋼在H2SO4 / HCl水溶液中選擇性溶解現象

Selective Dissolution of 2205 Duplex Stainless Steel in H2SO4 / HCl Solution

由於雙相不銹鋼兩相的化學組成差異，使其在某些環境中會有選擇性溶解的現象發生。本研究結果顯示，2205雙相不銹鋼在H2SO4 / HC l混酸水溶液中所得之動電位極化曲線中有活性–鈍態轉換的反應生成，而此反應中包含兩個明顯的陽極峰，這兩個陽極峰的生成與雙相不銹鋼中兩相於混酸水溶液中的選擇性溶解有關。分別在不同的陽極峰電位進行定電位測試，發現在較低電位的陽極峰下，肥粒體相被優先侵蝕；而在電位較高的陽極峰電位下，則發現沃斯田體相為優先被侵蝕的對象。另外，2205雙相不銹鋼在H2SO4 / HC l混酸水溶液中，肥粒體與沃斯田體相發生選擇性溶解所造成的電流密度值，分別隨著溶液中H2SO4與HC l濃度的增加，而有上升的趨勢。

The difference in chemical composition between the two constituent phases in duplex stainless steel (DSS) could result in the occurrence of selective dissolution. In this study, two obvious peaks in the active-to-passive transition zone caused by selective dissolution in the mixed H2SO4/HCl solution of 2205 DSS was found. Microstructure analysis and phase identification were performed after potentiostatic test in these two separate potential using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The peak appeared at a lower potential region was associated with the preferential dissolution of ferrite phase while that for austenite at a higher potential. In the mixed H2SO4/HCl solution, the dissolution of ferrite was favored by increasing the concentration of H2SO4, while enhanced dissolution of austenite was found at a high concentration HCl.