{"title":"Masthead: Materials and Corrosion. 3/2022","authors":"","doi":"10.1002/maco.202270032","DOIUrl":"https://doi.org/10.1002/maco.202270032","url":null,"abstract":"","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86299154","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, B. Jegdić, Jovana Pejić, Milena Milošević, A. Marinković, Bojana M. Radojković
The new environmentally friendly corrosion inhibitor Ce‐citrate was analyzed in 0.05 M NaCl solution on the AISI 4130 steel. For comparison, corrosion inhibitor Ce‐chloride is tested in the same concentration as Ce‐citrate (0.3 mM). Inhibitor efficiencies were determined by applying electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The results of electrochemical measurements, the contact angle measurements, as well as the surface appearance of the specimens after the immersion in the inhibitive NaCl solution for 96 h confirmed that the new environmentally friendly inhibitor (Ce‐citrate) has a significantly higher protective ability than the Ce‐chloride. The protective ability of Ce‐citrate increases over time, according to the proposed mechanism of its action. In the inhibitive layer formed in NaCl solution containing Ce‐citrate, XPS analysis revealed the presence of cerium in oxidation states CeIII and CeIV, citrate anions (carboxyl O–C═O group as well as C–OH and C–C and C–H bonds), oxide, hydroxide, and oxyhydroxide of iron (mainly FeOOH and Fe2O3). The mechanism of inhibitory action of Ce‐citrate was proposed and analyzed in detail.
在0.05 M NaCl溶液中对新型环保型缓蚀剂柠檬酸铈(Ce‐citrate)在AISI 4130钢上进行了分析。为了进行比较，缓蚀剂氯化铈在与柠檬酸铈(0.3 mM)相同浓度下进行测试。通过电化学阻抗谱和动电位极化测量来确定缓蚀剂的效率。电化学测量、接触角测量以及样品在NaCl溶液中浸泡96 h后的表面形貌均证实了新型环保型缓蚀剂(柠檬酸铈)的保护能力明显高于氯化铈。根据提出的作用机制，柠檬酸铈的保护能力随着时间的推移而增加。在含有柠檬酸Ce的NaCl溶液中形成的抑制层中，XPS分析发现铈在氧化态CeIII和CeIV、柠檬酸阴离子(羧基O - c = O基团以及C-OH和C-C和C-H键)、铁的氧化物、氢氧化物和氢氧化物(主要是FeOOH和Fe2O3)中存在。提出并详细分析了柠檬酸铈的抑制作用机理。
{"title":"Analysis of inhibitory properties of Ce‐citrate as a green corrosion inhibitor of low alloy steel in neutral chloride solution","authors":"Dunja Marunkić, B. Jegdić, Jovana Pejić, Milena Milošević, A. Marinković, Bojana M. Radojković","doi":"10.1002/maco.202213079","DOIUrl":"https://doi.org/10.1002/maco.202213079","url":null,"abstract":"The new environmentally friendly corrosion inhibitor Ce‐citrate was analyzed in 0.05 M NaCl solution on the AISI 4130 steel. For comparison, corrosion inhibitor Ce‐chloride is tested in the same concentration as Ce‐citrate (0.3 mM). Inhibitor efficiencies were determined by applying electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The results of electrochemical measurements, the contact angle measurements, as well as the surface appearance of the specimens after the immersion in the inhibitive NaCl solution for 96 h confirmed that the new environmentally friendly inhibitor (Ce‐citrate) has a significantly higher protective ability than the Ce‐chloride. The protective ability of Ce‐citrate increases over time, according to the proposed mechanism of its action. In the inhibitive layer formed in NaCl solution containing Ce‐citrate, XPS analysis revealed the presence of cerium in oxidation states CeIII and CeIV, citrate anions (carboxyl O–C═O group as well as C–OH and C–C and C–H bonds), oxide, hydroxide, and oxyhydroxide of iron (mainly FeOOH and Fe2O3). The mechanism of inhibitory action of Ce‐citrate was proposed and analyzed in detail.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"118 1","pages":"1286 - 1297"},"PeriodicalIF":0.0,"publicationDate":"2022-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81780177","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 high‐temperature sulfur corrosion resistance of S30432 and TP310HCbN typically used in the superheater and reheater of a 620°C ultra‐supercritical boiler is investigated in this study. Samples coated with coal ash are placed in a device filled with simulated flue gas at 650°C and 700°C, respectively, for 2000 h. The samples are then analyzed through X‐ray diffraction, scanning electron microscopy, and energy‐dispersive spectroscopy. S30432 is mainly oxidized under 650°C and 0.2% SO2 volume concentration, and the weight reduction is 6.6 mg cm−2. However, under 700°C and 0.3% SO2 volume concentration, severe sulfidation reaction occurs, sharply accelerating high‐temperature corrosion. As a result, weight reduction up to 41.8 mg cm−2 occurs. Although sulfidation reaction also occurs in TP310HCbN, there is no serious corrosion; the corrosion rate reduces in the later stages of the experiment, and a weight increase of 2.4 mg cm−2 is observed. After 11 520 h of the actual operation of the 1000 MW 620°C boiler, there is no obvious high‐temperature corrosion in the high‐temperature areas without coke‐block adhesion. These results indicate that S30432 and TP310HCbN satisfy the requirements of 620°C ultra‐supercritical boilers burning high‐sulfur coal.
{"title":"High‐temperature corrosion behavior of S30432 and TP310HCbN coatings in simulated 620°C ultra‐supercritical boiler coal ash/gas environment","authors":"Yugang Liu, Yinhe Liu, Chunhong Mo, Minqiang Zhang, Meng Dong, Shaocheng Pan, Shenming Ran","doi":"10.1002/maco.202113014","DOIUrl":"https://doi.org/10.1002/maco.202113014","url":null,"abstract":"The high‐temperature sulfur corrosion resistance of S30432 and TP310HCbN typically used in the superheater and reheater of a 620°C ultra‐supercritical boiler is investigated in this study. Samples coated with coal ash are placed in a device filled with simulated flue gas at 650°C and 700°C, respectively, for 2000 h. The samples are then analyzed through X‐ray diffraction, scanning electron microscopy, and energy‐dispersive spectroscopy. S30432 is mainly oxidized under 650°C and 0.2% SO2 volume concentration, and the weight reduction is 6.6 mg cm−2. However, under 700°C and 0.3% SO2 volume concentration, severe sulfidation reaction occurs, sharply accelerating high‐temperature corrosion. As a result, weight reduction up to 41.8 mg cm−2 occurs. Although sulfidation reaction also occurs in TP310HCbN, there is no serious corrosion; the corrosion rate reduces in the later stages of the experiment, and a weight increase of 2.4 mg cm−2 is observed. After 11 520 h of the actual operation of the 1000 MW 620°C boiler, there is no obvious high‐temperature corrosion in the high‐temperature areas without coke‐block adhesion. These results indicate that S30432 and TP310HCbN satisfy the requirements of 620°C ultra‐supercritical boilers burning high‐sulfur coal.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"32 1","pages":"1222 - 1235"},"PeriodicalIF":0.0,"publicationDate":"2022-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89959922","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}
R. Baldan, L. Latu-Romain, Y. Wouters, N. Chaia, L. B. Alkmin, A. M. S. Sousa Malafaia
Superalloys are widely employed at high temperatures for structural applications. Hence, knowledge about the oxidation of these materials is essential. However, the literature is scanty when it comes to some families of superalloys. The purpose of this study was therefore to analyze the MAR‐M246 polycrystalline alloy in isothermal short‐term tests at 800°C and 1000°C for up to 240 h. Thermodynamic simulations were performed to evaluate the material's phase stability as a function of temperature and to assess the expected phases in response to oxygen pressure. The oxidized samples were characterized by SEM‐EDS and DRX, which revealed a tendency for scaling of oxidized material, particularly at temperatures of 1000°C. Nevertheless, protective layers of Cr2O3 and Al2O3 oxides were formed, which enabled the formation of fairly thin oxide layers, in addition to NiO and complex oxides. The region of the metallic substrate close to the oxide layer underwent aluminum depletion, causing the gamma‐prime phase to disappear, as well as formation of aluminum oxides and titanium nitrides. Last, a good correlation was found between the thermodynamic simulations and the oxides that were formed.
{"title":"Isothermal short‐term oxidation behavior of MAR‐M246 nickel‐based superalloy at 800°C and 1000°C","authors":"R. Baldan, L. Latu-Romain, Y. Wouters, N. Chaia, L. B. Alkmin, A. M. S. Sousa Malafaia","doi":"10.1002/maco.202112931","DOIUrl":"https://doi.org/10.1002/maco.202112931","url":null,"abstract":"Superalloys are widely employed at high temperatures for structural applications. Hence, knowledge about the oxidation of these materials is essential. However, the literature is scanty when it comes to some families of superalloys. The purpose of this study was therefore to analyze the MAR‐M246 polycrystalline alloy in isothermal short‐term tests at 800°C and 1000°C for up to 240 h. Thermodynamic simulations were performed to evaluate the material's phase stability as a function of temperature and to assess the expected phases in response to oxygen pressure. The oxidized samples were characterized by SEM‐EDS and DRX, which revealed a tendency for scaling of oxidized material, particularly at temperatures of 1000°C. Nevertheless, protective layers of Cr2O3 and Al2O3 oxides were formed, which enabled the formation of fairly thin oxide layers, in addition to NiO and complex oxides. The region of the metallic substrate close to the oxide layer underwent aluminum depletion, causing the gamma‐prime phase to disappear, as well as formation of aluminum oxides and titanium nitrides. Last, a good correlation was found between the thermodynamic simulations and the oxides that were formed.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"10 1","pages":"1236 - 1247"},"PeriodicalIF":0.0,"publicationDate":"2022-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82371313","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}
Mogomotsi Leshetla, D. Klenam, J. Merwe, Herman Potgieter, D. Whitefield, M. Bodunrin
In this study, experimental Ti–6Al–1V–3Fe, Ti–4.5Al–1V–3Fe, and Ti–3Fe alloys, as well as commercial Ti–6Al–4V alloy that were scaled up utilizing vacuum induction melting technology, were assessed for corrosion performance in simulated body fluids. The selected simulated body fluids were 0.9 wt% NaCl solution and Hanks balanced salt solution (HBSS). Open circuit potential and linear polarization scans were performed to understand the corrosion performance of the alloys. The surface of the alloys was examined before and after exposure to corrosive solutions using scanning electron microscopy. The results show that all the alloys exhibit good corrosion performance in simulated body fluids. The corrosion rates were less than 0.5 mm/year. Owing to higher corrosion potential and lower corrosion rate, Ti–6Al–1V–3Fe and Ti–4.5Al–1V–3Fe had the best resistance to corrosion in 0.9 wt% NaCl and HBSS, respectively. All the alloys consist of a fully lamellar structure with α and β phases. There was no evidence of severe deterioration on the exposed surface of alloys in the simulated body fluids.
{"title":"Corrosion resistance of iron‐containing experimental titanium alloys exposed to simulated body fluids","authors":"Mogomotsi Leshetla, D. Klenam, J. Merwe, Herman Potgieter, D. Whitefield, M. Bodunrin","doi":"10.1002/maco.202213076","DOIUrl":"https://doi.org/10.1002/maco.202213076","url":null,"abstract":"In this study, experimental Ti–6Al–1V–3Fe, Ti–4.5Al–1V–3Fe, and Ti–3Fe alloys, as well as commercial Ti–6Al–4V alloy that were scaled up utilizing vacuum induction melting technology, were assessed for corrosion performance in simulated body fluids. The selected simulated body fluids were 0.9 wt% NaCl solution and Hanks balanced salt solution (HBSS). Open circuit potential and linear polarization scans were performed to understand the corrosion performance of the alloys. The surface of the alloys was examined before and after exposure to corrosive solutions using scanning electron microscopy. The results show that all the alloys exhibit good corrosion performance in simulated body fluids. The corrosion rates were less than 0.5 mm/year. Owing to higher corrosion potential and lower corrosion rate, Ti–6Al–1V–3Fe and Ti–4.5Al–1V–3Fe had the best resistance to corrosion in 0.9 wt% NaCl and HBSS, respectively. All the alloys consist of a fully lamellar structure with α and β phases. There was no evidence of severe deterioration on the exposed surface of alloys in the simulated body fluids.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"35 1","pages":"1298 - 1307"},"PeriodicalIF":0.0,"publicationDate":"2022-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79777240","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}
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}
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