To clarify the corrosion mechanism of 15CrMo in saline (Na2SO4) steam, the experiments were conducted on a novel setup. The samples were analyzed by scanning electron microscope and X‐ray photoelectron spectroscopy. The results indicate that insoluble sulfide, FexSy, would form on the gas‐phase corroded surface while it would not occur on the liquid‐phase corroded surface. The salinity of water/steam has a destructive effect on hydrogen bonds. Compared with deionized steam/water, salinity accelerates the corrosion of steel in two ways electric current intensification in primary cell and energy promotion of the solution system. FeOOH does not change obviously with the increase of salt concentration. The relative variation values of FeOOH content with salt concentration are only 2.43% (gas) and 3.40% (liquid), respectively. Besides, the FeOOH content on the liquid‐phase corroded surface is much greater than that on the gas‐phase corroded surface regardless of the salt concentration. The content of Fe3O4 in the gas/liquid phase decreases from 17.01%/24.58% to 6.02%/18.30%. The Fe2O3 content in the gas/liquid phase increases from 40.12%/9.85% to 73.62%/17.05%.
{"title":"A study on corrosion mechanism of 15CrMo in saline (Na2SO4) steam at high temperature","authors":"B. Bai, L. Deng, D. Che","doi":"10.1002/maco.202112687","DOIUrl":"https://doi.org/10.1002/maco.202112687","url":null,"abstract":"To clarify the corrosion mechanism of 15CrMo in saline (Na2SO4) steam, the experiments were conducted on a novel setup. The samples were analyzed by scanning electron microscope and X‐ray photoelectron spectroscopy. The results indicate that insoluble sulfide, FexSy, would form on the gas‐phase corroded surface while it would not occur on the liquid‐phase corroded surface. The salinity of water/steam has a destructive effect on hydrogen bonds. Compared with deionized steam/water, salinity accelerates the corrosion of steel in two ways electric current intensification in primary cell and energy promotion of the solution system. FeOOH does not change obviously with the increase of salt concentration. The relative variation values of FeOOH content with salt concentration are only 2.43% (gas) and 3.40% (liquid), respectively. Besides, the FeOOH content on the liquid‐phase corroded surface is much greater than that on the gas‐phase corroded surface regardless of the salt concentration. The content of Fe3O4 in the gas/liquid phase decreases from 17.01%/24.58% to 6.02%/18.30%. The Fe2O3 content in the gas/liquid phase increases from 40.12%/9.85% to 73.62%/17.05%.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"20 1","pages":"971 - 979"},"PeriodicalIF":0.0,"publicationDate":"2022-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78581659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The effect of 1.5% Cr on the corrosion resistance of low‐alloy steel in a simulated mine environment was studied. To clarify the effect of Cr on the corrosion of low‐alloy steel in the wet environment at the initial stage of corrosion, salt spray corrosion tests were performed to simulate the corrosion process in the field, and the bare steel and corrosion products were characterized. The results showed that the addition of 1.5% Cr reduced the surface potential and the kinetic tendency of the corrosion reaction, making the corrosion rate at the initial stage of the test lower than anticipated. An increase in Cr content significantly elevates the level of α‐FeOOH. The corrosion product film (CPF) had a bilayer structure, with α‐FeOOH of Cr‐rich and Cr(OH)3 were found in the inner layer and at the junction of the inner and outer layer. The CPF had a dense structure that effectively reduced electrochemical reaction activity and improved corrosion resistance.
{"title":"Effect of alloyed Cr on corrosion behavior of low‐alloy steel in wet atmosphere","authors":"Rui Yuan, Hui-bin Wu, Yang Gu","doi":"10.1002/maco.202112715","DOIUrl":"https://doi.org/10.1002/maco.202112715","url":null,"abstract":"The effect of 1.5% Cr on the corrosion resistance of low‐alloy steel in a simulated mine environment was studied. To clarify the effect of Cr on the corrosion of low‐alloy steel in the wet environment at the initial stage of corrosion, salt spray corrosion tests were performed to simulate the corrosion process in the field, and the bare steel and corrosion products were characterized. The results showed that the addition of 1.5% Cr reduced the surface potential and the kinetic tendency of the corrosion reaction, making the corrosion rate at the initial stage of the test lower than anticipated. An increase in Cr content significantly elevates the level of α‐FeOOH. The corrosion product film (CPF) had a bilayer structure, with α‐FeOOH of Cr‐rich and Cr(OH)3 were found in the inner layer and at the junction of the inner and outer layer. The CPF had a dense structure that effectively reduced electrochemical reaction activity and improved corrosion resistance.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"11 1","pages":"918 - 931"},"PeriodicalIF":0.0,"publicationDate":"2022-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85097437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High‐temperature corrosion was studied under multiple chemical loads on ferritic‐austenitic model alloys (Fe–13Cr, Fe–18Cr–12Ni, and Fe‐25Cr–20Ni) with KCl deposit under 0.5% SO2 ${text{SO}}_{2}$ /99.5% Ar gas atmosphere at 560°C $560^circ {rm{C}}$ . Postexposure characterization was done by X‐ray diffraction and scanning electron microscopy. In a pure SO2 ${text{SO}}_{2}$ /Ar environment a protective Cr2O3 ${text{Cr}}_{2}{{rm{O}}}_{3}$ scale was formed by all samples. The introduction of KCl deposits causes the scale to be nonprotective and multilayered, consisting of CrS, FeS, Cr2O3,Fe3O4 ${text{Cr}}_{2}{{rm{O}}}_{3},{text{Fe}}_{3}{{rm{O}}}_{4}$ , and Fe2O3 ${text{Fe}}_{2}{{rm{O}}}_{3}$ . The impact of the microstructure and alloying elements is discussed.
{"title":"Effect of KCl deposits in high‐temperature corrosion on chromium‐rich steels in SO2‐containing atmosphere","authors":"Phillip Kingsbery, Christiane Stephan‐Scherb","doi":"10.1002/maco.202112901","DOIUrl":"https://doi.org/10.1002/maco.202112901","url":null,"abstract":"High‐temperature corrosion was studied under multiple chemical loads on ferritic‐austenitic model alloys (Fe–13Cr, Fe–18Cr–12Ni, and Fe‐25Cr–20Ni) with KCl deposit under 0.5% SO2 ${text{SO}}_{2}$ /99.5% Ar gas atmosphere at 560°C $560^circ {rm{C}}$ . Postexposure characterization was done by X‐ray diffraction and scanning electron microscopy. In a pure SO2 ${text{SO}}_{2}$ /Ar environment a protective Cr2O3 ${text{Cr}}_{2}{{rm{O}}}_{3}$ scale was formed by all samples. The introduction of KCl deposits causes the scale to be nonprotective and multilayered, consisting of CrS, FeS, Cr2O3,Fe3O4 ${text{Cr}}_{2}{{rm{O}}}_{3},{text{Fe}}_{3}{{rm{O}}}_{4}$ , and Fe2O3 ${text{Fe}}_{2}{{rm{O}}}_{3}$ . The impact of the microstructure and alloying elements is discussed.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"1 1","pages":"758 - 770"},"PeriodicalIF":0.0,"publicationDate":"2022-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82949960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The aim of this study is to elucidate suitable methods of corrosion monitoring for chloride‐induced rebar corrosion in cracked concrete. Depolarization gradients and transients provide evidence for the electrode kinetics at the steel–concrete interface and the geometry of the macrocell. In the present study, a set of cracked, short‐term chloride‐exposed, reinforced concrete specimens is investigated in terms of their corrosion activity. Primarily, the depolarization behavior was observed by short‐term high‐frequency measurements, allowing for cost‐effective measurement campaigns and robust results. All measurement intervals are split apart via a gradient analysis to enable a congruent, numerical transient analysis. Since the geometry of macrocells in rebar corrosion follows the model of a series of ohmic resistances with a parallel connection of a diffusion‐controlled capacitor and an ohmic resistance, the transient of each depolarization curve with unit time in seconds provides evidence for the present electrode kinetics and macrocell geometry. According to the time, which is consumed until a certain state of depolarization is reached, transient modeling can be used to predict corrosion activity as a function of chloride ingress.
{"title":"Transient and gradient analyses of depolarization criteria. Valuable tools in chloride‐induced rebar corrosion monitoring","authors":"Christoph Zausinger, K. Osterminski, C. Gehlen","doi":"10.1002/maco.202112839","DOIUrl":"https://doi.org/10.1002/maco.202112839","url":null,"abstract":"The aim of this study is to elucidate suitable methods of corrosion monitoring for chloride‐induced rebar corrosion in cracked concrete. Depolarization gradients and transients provide evidence for the electrode kinetics at the steel–concrete interface and the geometry of the macrocell. In the present study, a set of cracked, short‐term chloride‐exposed, reinforced concrete specimens is investigated in terms of their corrosion activity. Primarily, the depolarization behavior was observed by short‐term high‐frequency measurements, allowing for cost‐effective measurement campaigns and robust results. All measurement intervals are split apart via a gradient analysis to enable a congruent, numerical transient analysis. Since the geometry of macrocells in rebar corrosion follows the model of a series of ohmic resistances with a parallel connection of a diffusion‐controlled capacitor and an ohmic resistance, the transient of each depolarization curve with unit time in seconds provides evidence for the present electrode kinetics and macrocell geometry. According to the time, which is consumed until a certain state of depolarization is reached, transient modeling can be used to predict corrosion activity as a function of chloride ingress.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"39 1","pages":"932 - 939"},"PeriodicalIF":0.0,"publicationDate":"2022-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85915068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Organic repair coatings are applied to repair areas of previously coated low‐carbon steel samples, and the samples are exposed to the splash zone in an offshore environment (Helgoland, North Sea) for 57 months. The volume loss of the steel underneath the delaminated coating is estimated with a three‐dimensional optical stripe line projection. The samples show a small variation in the degree of delamination (22%) only. The steel volume loss values, in contrast, range between 164 × 109 and 320 × 109 µm³, which is a variation of 196%. The degree of delamination of the scribed coatings does not mirror the corrosion of the steel underneath the delaminated sections. The coating with the widest degree of delamination exhibits the lowest steel volume loss due to corrosion. A good scribe performance of a coating is, therefore, no guarantee for a low corrosion loss nor for a low local corrosion depth in the steels to be protected.
{"title":"The corrosion of carbon steel under delaminating repair coatings after long‐term marine splash zone exposure","authors":"A. Momber, Andreas Krenz, Sascha Buchbach","doi":"10.1002/maco.202112942","DOIUrl":"https://doi.org/10.1002/maco.202112942","url":null,"abstract":"Organic repair coatings are applied to repair areas of previously coated low‐carbon steel samples, and the samples are exposed to the splash zone in an offshore environment (Helgoland, North Sea) for 57 months. The volume loss of the steel underneath the delaminated coating is estimated with a three‐dimensional optical stripe line projection. The samples show a small variation in the degree of delamination (22%) only. The steel volume loss values, in contrast, range between 164 × 109 and 320 × 109 µm³, which is a variation of 196%. The degree of delamination of the scribed coatings does not mirror the corrosion of the steel underneath the delaminated sections. The coating with the widest degree of delamination exhibits the lowest steel volume loss due to corrosion. A good scribe performance of a coating is, therefore, no guarantee for a low corrosion loss nor for a low local corrosion depth in the steels to be protected.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"9 1","pages":"897 - 902"},"PeriodicalIF":0.0,"publicationDate":"2022-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84193760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The corrosion behavior of a galvanic coupling consisting of a 7075‐T6‐aluminum alloy and a low‐carbon low‐manganese microalloyed dual‐phase steel was studied in a 3% NaCl aqueous solution at room temperature. Corrosion behavior of the individual materials was assessed from potentiodynamic polarization and electrochemical impedance spectroscopy measurements conducted on the individual couple components. The corrosion rate of the individual samples was found to be seven times larger on the microalloyed steel than on the aluminum alloy. From a comparison of corrosion current densities, the galvanic couple was found to sustain a nonsignificant galvanic effect—the latter in contrast to what may be determined considering differences in their respective corrosion potentials. According to the applied mixed‐potential theory and the zero‐resistance‐ammeter measurements performed directly on the galvanic couple, the aluminum‐alloy acted as the anodic member of the galvanic couple. Such behavior was justified by kinetic parameters rather than thermodynamic ones, considering the favorable rate of the oxygen reduction reaction on the microalloyed steel surface.
{"title":"Assessment of the galvanic corrosion of bi‐metallic couple 7075‐T6‐aluminum alloy/microalloyed dual‐phase steel","authors":"Vianey Torres, R. Mayén‐Mondragón, Juan Genesca","doi":"10.1002/maco.202112934","DOIUrl":"https://doi.org/10.1002/maco.202112934","url":null,"abstract":"The corrosion behavior of a galvanic coupling consisting of a 7075‐T6‐aluminum alloy and a low‐carbon low‐manganese microalloyed dual‐phase steel was studied in a 3% NaCl aqueous solution at room temperature. Corrosion behavior of the individual materials was assessed from potentiodynamic polarization and electrochemical impedance spectroscopy measurements conducted on the individual couple components. The corrosion rate of the individual samples was found to be seven times larger on the microalloyed steel than on the aluminum alloy. From a comparison of corrosion current densities, the galvanic couple was found to sustain a nonsignificant galvanic effect—the latter in contrast to what may be determined considering differences in their respective corrosion potentials. According to the applied mixed‐potential theory and the zero‐resistance‐ammeter measurements performed directly on the galvanic couple, the aluminum‐alloy acted as the anodic member of the galvanic couple. Such behavior was justified by kinetic parameters rather than thermodynamic ones, considering the favorable rate of the oxygen reduction reaction on the microalloyed steel surface.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"6 1","pages":"940 - 949"},"PeriodicalIF":0.0,"publicationDate":"2022-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82123383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jie-zhen Hu, Huan Huang, P. Deng, Gui Wang, Mingfa Wu, Wenjuan Liu
In this study, the galvanic corrosion behavior of the side surface of titanium‐clad steel plate (TCSP) and below the defects, which penetrate through the titanium layer of TCSP, have been focused on. Electrochemical corrosion tests and infinite focus three‐dimensional measurement results revealed that galvanic corrosion on the side of TCSP will lead to widespread pitting of the steel, and the distribution positions of pits in splash, tidal, and submerged zones are different. Severe corrosion occurs below the defects in the titanium layer of TCSP, and the larger the defect, the deeper the corrosion depth, but TCSP with smaller defects have larger corrosion width on the Ti‐Stl line (the joint between the titanium and steel). This shows that the size of the defect will influence the density of corrosion products and the effect of TCSP defect internal corrosion on titanium layer peeling is extremely limited.
{"title":"Galvanic corrosion behavior of titanium‐clad steel plate in the marine environment","authors":"Jie-zhen Hu, Huan Huang, P. Deng, Gui Wang, Mingfa Wu, Wenjuan Liu","doi":"10.1002/maco.202113019","DOIUrl":"https://doi.org/10.1002/maco.202113019","url":null,"abstract":"In this study, the galvanic corrosion behavior of the side surface of titanium‐clad steel plate (TCSP) and below the defects, which penetrate through the titanium layer of TCSP, have been focused on. Electrochemical corrosion tests and infinite focus three‐dimensional measurement results revealed that galvanic corrosion on the side of TCSP will lead to widespread pitting of the steel, and the distribution positions of pits in splash, tidal, and submerged zones are different. Severe corrosion occurs below the defects in the titanium layer of TCSP, and the larger the defect, the deeper the corrosion depth, but TCSP with smaller defects have larger corrosion width on the Ti‐Stl line (the joint between the titanium and steel). This shows that the size of the defect will influence the density of corrosion products and the effect of TCSP defect internal corrosion on titanium layer peeling is extremely limited.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"32 1","pages":"887 - 896"},"PeriodicalIF":0.0,"publicationDate":"2022-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88488379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dunja Marunkić, Jovana Pejić, B. Jegdić, A. Marinković, Bojana M. Radojković
The corrosion behaviour of high‐strength AA7075 aluminium alloy in NaCl solution, without and in the presence of environmentally friendly corrosion inhibitors (Ce‐chloride and Ce‐citrate) in low concentrations (<0.5 mM), was analysed. The degree of precipitation of the solid solution of AA7075 alloy was determined by measuring the electrical conductivity, while the surface morphology and appearance of intermetallic compounds before and after corrosion testing were analysed by SEM/EDS method. The general corrosion resistance of the tested alloy in NaCl solution and the degree of the inhibitory effect of the corrosion inhibitors were determined on the basis of electrochemical impedance spectroscopy and polarization measurements, while resistance to pit formation on the bases of Epit. AA7075 alloy showed high resistance to general corrosion in the presence of both tested inhibitors, while resistance to pit formation was significantly higher in the presence of Ce‐citrate (concentration 0.5 mM). Also, Ce‐citrate present in NaCl solution at lower concentrations provides satisfactory resistance of AA7075 alloy to general and pitting corrosion. A mechanism of protective action of Ce‐citrate inhibitor has been proposed.
{"title":"Cerium citrate as ecologically friendly corrosion inhibitor for AA7075 alloy","authors":"Dunja Marunkić, Jovana Pejić, B. Jegdić, A. Marinković, Bojana M. Radojković","doi":"10.1002/maco.202112900","DOIUrl":"https://doi.org/10.1002/maco.202112900","url":null,"abstract":"The corrosion behaviour of high‐strength AA7075 aluminium alloy in NaCl solution, without and in the presence of environmentally friendly corrosion inhibitors (Ce‐chloride and Ce‐citrate) in low concentrations (<0.5 mM), was analysed. The degree of precipitation of the solid solution of AA7075 alloy was determined by measuring the electrical conductivity, while the surface morphology and appearance of intermetallic compounds before and after corrosion testing were analysed by SEM/EDS method. The general corrosion resistance of the tested alloy in NaCl solution and the degree of the inhibitory effect of the corrosion inhibitors were determined on the basis of electrochemical impedance spectroscopy and polarization measurements, while resistance to pit formation on the bases of Epit. AA7075 alloy showed high resistance to general corrosion in the presence of both tested inhibitors, while resistance to pit formation was significantly higher in the presence of Ce‐citrate (concentration 0.5 mM). Also, Ce‐citrate present in NaCl solution at lower concentrations provides satisfactory resistance of AA7075 alloy to general and pitting corrosion. A mechanism of protective action of Ce‐citrate inhibitor has been proposed.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"82 1","pages":"950 - 960"},"PeriodicalIF":0.0,"publicationDate":"2022-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73894774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Shi, Xixun Shen, Gaofei Liang, Yanshaozuo Zhu, Qunjie Xu
The acid‐resistant steel represented by 09CrCuSb (ND) steel that is widely used in flue gas treatment systems is easily prone to mixed‐acid dew point corrosion in the low‐temperature flue gas environment. To improve the corrosion resistance of ND steel in a low‐temperature dew point corrosion environment, here, a chromium–myristate hybrid (CMH) superhydrophobic coating is proposed as a low‐temperature dew point corrosion protective coating for the ND steel substrate. This superhydrophobic coating is deposited on the ND steel substrate (preplated dark nickel as a transition layer) by one‐step direct current electrodeposition. The electrochemical analysis from potentiodynamic polarization and electrochemical impedance spectroscopy and the immersion test show that the CMH superhydrophobic coating can significantly improve the corrosion resistance of the ND substrate. Therefore, the present study provides a feasible strategy for preventing the mixed‐acid dew point corrosion of ND steel in the low‐temperature zone.
{"title":"The superhydrophobic coating with low‐temperature dew point corrosion resistance on an acid‐resistant steel substrate prepared by the electrodeposition method","authors":"B. Shi, Xixun Shen, Gaofei Liang, Yanshaozuo Zhu, Qunjie Xu","doi":"10.1002/maco.202112832","DOIUrl":"https://doi.org/10.1002/maco.202112832","url":null,"abstract":"The acid‐resistant steel represented by 09CrCuSb (ND) steel that is widely used in flue gas treatment systems is easily prone to mixed‐acid dew point corrosion in the low‐temperature flue gas environment. To improve the corrosion resistance of ND steel in a low‐temperature dew point corrosion environment, here, a chromium–myristate hybrid (CMH) superhydrophobic coating is proposed as a low‐temperature dew point corrosion protective coating for the ND steel substrate. This superhydrophobic coating is deposited on the ND steel substrate (preplated dark nickel as a transition layer) by one‐step direct current electrodeposition. The electrochemical analysis from potentiodynamic polarization and electrochemical impedance spectroscopy and the immersion test show that the CMH superhydrophobic coating can significantly improve the corrosion resistance of the ND substrate. Therefore, the present study provides a feasible strategy for preventing the mixed‐acid dew point corrosion of ND steel in the low‐temperature zone.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"36 1","pages":"903 - 917"},"PeriodicalIF":0.0,"publicationDate":"2022-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85112183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. V. Harinath, P. Chandramohan, B. Anandkumar, T. Mohan, S. Rangarajan, S. Albert
Many studies have revealed that Hastelloy‐N is the most suitable material for molten FLiNaK salt application. However, due to the nonavailability and high cost of Hastelloy‐N, Incoloy‐800HT is being considered as an alternate material. Corrosion studies were carried out on Incoloy‐800HT in vacuum‐dried molten FLiNaK salt at 650°C and 750°C for 100, 250, 500 and 1000 h. The exposed specimens were examined for weight loss and subjected to surface analysis using techniques like metallography, confocal laser scanning microscopy, X‐ray diffraction and laser Raman spectroscopy. The results revealed that the weight loss and depth of attack are less in specimens exposed to 650°C than those exposed to 750°C, and there is no evidence of any localised attack at both the temperatures. Chemical analysis of the used salt showed higher Cr and Fe contents than that in fresh salt, indicating dealloying of elements like Cr and Fe from Incoloy‐800HT specimens during exposure to molten FLiNaK salt. Oxides rich in Fe and Cr with spinel‐type crystal structures were identified on the exposed surfaces. From the results, it could be concluded that though there was considerable corrosion of Incoloy‐800HT, the material may be used in static molten FLiNaK salt systems with limited design life restricted to a temperature of 650°C by giving appropriate corrosion allowance.
{"title":"Degradation of Incoloy‐800HT in molten FLiNaK salt at high temperatures","authors":"Y. V. Harinath, P. Chandramohan, B. Anandkumar, T. Mohan, S. Rangarajan, S. Albert","doi":"10.1002/maco.202112758","DOIUrl":"https://doi.org/10.1002/maco.202112758","url":null,"abstract":"Many studies have revealed that Hastelloy‐N is the most suitable material for molten FLiNaK salt application. However, due to the nonavailability and high cost of Hastelloy‐N, Incoloy‐800HT is being considered as an alternate material. Corrosion studies were carried out on Incoloy‐800HT in vacuum‐dried molten FLiNaK salt at 650°C and 750°C for 100, 250, 500 and 1000 h. The exposed specimens were examined for weight loss and subjected to surface analysis using techniques like metallography, confocal laser scanning microscopy, X‐ray diffraction and laser Raman spectroscopy. The results revealed that the weight loss and depth of attack are less in specimens exposed to 650°C than those exposed to 750°C, and there is no evidence of any localised attack at both the temperatures. Chemical analysis of the used salt showed higher Cr and Fe contents than that in fresh salt, indicating dealloying of elements like Cr and Fe from Incoloy‐800HT specimens during exposure to molten FLiNaK salt. Oxides rich in Fe and Cr with spinel‐type crystal structures were identified on the exposed surfaces. From the results, it could be concluded that though there was considerable corrosion of Incoloy‐800HT, the material may be used in static molten FLiNaK salt systems with limited design life restricted to a temperature of 650°C by giving appropriate corrosion allowance.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"443 1","pages":"771 - 783"},"PeriodicalIF":0.0,"publicationDate":"2022-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86856868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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