Alloys containing chromium （Cr） and molybdenum （Mo）, as the major alloying elements, are widely used in various industries where the material experiences corrosive environments. Chromium （Cr）, when added in an o...Alloys containing chromium （Cr） and molybdenum （Mo）, as the major alloying elements, are widely used in various industries where the material experiences corrosive environments. Chromium （Cr）, when added in an optimum amount, forms a Cr203 passive film which protects the underlying metal in aggressive solutions. Molybdenum （Mo） forms its oxides in the low pH solutions, thus, enhances the uniform corrosion resistance of an alloy in reducing acids and assists in inhibition to localized corrosion. Minor alloying elements, like tungsten （W） and copper （Cu）, also improve the overall corrosion resistance of an alloy in specific solutions. In the present study, corrosion resistance behavior of commercial iron- based alloys （316L SS, 254 SMO and 20Cb3） and nickel-based alloys （Mone1400, Alloy 625 and C-276） was studied in the acidic solutions. While the corrosion behavior of wrought alloys has been widely studied, there is little to no information on the corrosion performance of their welds, typically being the weak regions for corrosion initiation and propagation. Therefore, an attempt was undertaken to investigate the uniform and localized corrosion performance of base metal, simulated heat-affected zone and all-weld-metal samples of a Ni-Cr-Mo-W alloy, C-276. The study was conducted in aggressive acidic solutions. Various corrosion and surface analytical techniques were utilized to analyze the results.展开更多
Nickel alloys containing optimum amounts of chromium （Cr）, molybdenum （Mo） and tungsten （W） are widely used in the chemical processing industries due to their tolerance to both oxidizing and reducing conditions....Nickel alloys containing optimum amounts of chromium （Cr）, molybdenum （Mo） and tungsten （W） are widely used in the chemical processing industries due to their tolerance to both oxidizing and reducing conditions. Unlike stainless steel （SS）, Ni-Cr-Mo （W） alloys exhibit remarkably high uniform corrosion resistance in major concentrated acids, like hydrochloric acid （HC1） and sulfuric acid （H2SO4）. A higher uniform corrosion resistance of Ni-Cr-Mo （W） alloys, compared to other alloys, in concentrated acids can be attributed to the formation of protective oxide film of Mo and W in reducing acids, and Cr oxide film in oxidizing solutions. The localized corrosion resistance of Ni-Cr-Mo （W） alloys, containing high amount Cr as well as Mo （or Mo ＋ W）, is also significantly higher than that of other commercially available alloys. The present study investigates the role of alloying elements, in nickel alloys, to uniform corrosion resistance in concentrated acids （HC1, HC1 ＋ oxidizing impurities and H2SO4） and localized corrosion performance in chloride-rich environments using ASTM G-48 test methodology. The corrosion tests were conducted on various alloys, and the results were analyzed using weight loss technique and electrochemical techniques, in conjunction with surface char- acterization tools.展开更多
文摘Alloys containing chromium （Cr） and molybdenum （Mo）, as the major alloying elements, are widely used in various industries where the material experiences corrosive environments. Chromium （Cr）, when added in an optimum amount, forms a Cr203 passive film which protects the underlying metal in aggressive solutions. Molybdenum （Mo） forms its oxides in the low pH solutions, thus, enhances the uniform corrosion resistance of an alloy in reducing acids and assists in inhibition to localized corrosion. Minor alloying elements, like tungsten （W） and copper （Cu）, also improve the overall corrosion resistance of an alloy in specific solutions. In the present study, corrosion resistance behavior of commercial iron- based alloys （316L SS, 254 SMO and 20Cb3） and nickel-based alloys （Mone1400, Alloy 625 and C-276） was studied in the acidic solutions. While the corrosion behavior of wrought alloys has been widely studied, there is little to no information on the corrosion performance of their welds, typically being the weak regions for corrosion initiation and propagation. Therefore, an attempt was undertaken to investigate the uniform and localized corrosion performance of base metal, simulated heat-affected zone and all-weld-metal samples of a Ni-Cr-Mo-W alloy, C-276. The study was conducted in aggressive acidic solutions. Various corrosion and surface analytical techniques were utilized to analyze the results.
文摘Nickel alloys containing optimum amounts of chromium （Cr）, molybdenum （Mo） and tungsten （W） are widely used in the chemical processing industries due to their tolerance to both oxidizing and reducing conditions. Unlike stainless steel （SS）, Ni-Cr-Mo （W） alloys exhibit remarkably high uniform corrosion resistance in major concentrated acids, like hydrochloric acid （HC1） and sulfuric acid （H2SO4）. A higher uniform corrosion resistance of Ni-Cr-Mo （W） alloys, compared to other alloys, in concentrated acids can be attributed to the formation of protective oxide film of Mo and W in reducing acids, and Cr oxide film in oxidizing solutions. The localized corrosion resistance of Ni-Cr-Mo （W） alloys, containing high amount Cr as well as Mo （or Mo ＋ W）, is also significantly higher than that of other commercially available alloys. The present study investigates the role of alloying elements, in nickel alloys, to uniform corrosion resistance in concentrated acids （HC1, HC1 ＋ oxidizing impurities and H2SO4） and localized corrosion performance in chloride-rich environments using ASTM G-48 test methodology. The corrosion tests were conducted on various alloys, and the results were analyzed using weight loss technique and electrochemical techniques, in conjunction with surface char- acterization tools.
