氯化鈉溶液中鐵錳鋁鉻鉬合金之電化學腐蝕性質及其鈍化膜研究

Abstract

過去已經有許多學者廣泛的研究過鐵-錳-鋁合金的電化學腐蝕行為。然而在他們的研究中, 於氯化鈉溶液內僅發現非鈍化現象及狹窄的鈍化區。在此次實驗中, 我們在鐵-錳-鋁-鉻-鉬-碳合金於氯化鈉溶液中發現具有穩定且寬廣的鈍化區, 其中鐵-28.5錳-9.0鋁-5.0鉻-1.0鉬-0.1碳合金的鈍化性質具有與17-4PH 不鏽鋼相近的抗腐蝕能力。 藉由電化學極化曲線分析, 於氯化鈉溶液添加鋁含量8.0%至9.0%較添加鉻含量5.0%至10.0%更能有效縮減活性至鈍化區範圍且更能降低鈍化電流。此外, 增加碳含量的效應對於鈍化的破壞較具有加凡尼腐蝕的雙相肥粒鐵及沃斯田鐵合金更為顯著。 我們利用X光光電子能譜分析發現鐵及錳原子量百分比於鈍化層中大量減少且具有較高含量的鋁, 鉻, 鉬及氧元素, 氧化物分別代表三氧化二鋁, 三氧化二鉻, 二氧化鉬及三氧化鉬。利用上述氧化物成分分析可知鐵-錳-鋁-鉻-鉬-碳合金具有安定且寬廣鈍化區的動機。外層鈍化區氧化二鋁, 三氧化二鉻, 二氧化鉬及三氧化鉬含量隨添加鋁, 鉻及1.0%鉬而增加。

In the past, many workers have extensively studied the electrochemical corrosion behavior of Fe-Mn-Al based alloys. Nevertheless, in their studies, either rather narrow or no passivation region could be observed in NaCl solution. In the present work, Fe-Mn-Al-Cr-Mo-C alloys with a stable and broad passivation region in NaCl solution have been developed by our workers, in which the passive property of the Fe-28.5Mn-9.0Al-5.0Cr-1.0Mo-0.1C alloy was similar to that of 17-4 PH stainless steel. From analyzing electrochemical polarization curves, the increase of aluminum content from 8.0% to 9.0% could move effectively narrowed the active to passive region and decreased the passive current (ip) than that of chromium content from 5.0% to 10.0% in NaCl solution. Besides, the effect of increasing carbon content in the passive property in NaCl solution was more detrimental than that of duplex ferrite (a) + austenite (g) phases microstructure forming a galvanic corrosion in Fe-Mn-Al-Cr-Mo-C alloys. The X-ray photoelectron spectroscopy (XPS) analysis indicated that the atomic percentages of iron and manganese abruptly decreased in the passive films. In contrast, the outer portion of the passive film was enriched in aluminum, chromium, molybdenum and oxygen elements, which were attributed to the presence of Al2O3, Cr2O3, MoO2 and MoO3 oxides. This is the reason why a stable and broad passivation region could be found in the present Fe-Mn-Al-Cr-Mo-C alloys. The volume fractions of Al2O3, Cr2O3, MoO2 and MoO3 in the outer portion of the passive film were significantly increased with increasing aluminum and chromium contents and addition of 1.0wt.%(0.53at.%) molybdenum.