The present work focused on investigating the corrosion behavior of NiCu low alloy steel in 0.05 M NaHCO_(3) solutions with different Cl−concentrations under the aerobic–anoxic condition.The results showed that NiCu ...The present work focused on investigating the corrosion behavior of NiCu low alloy steel in 0.05 M NaHCO_(3) solutions with different Cl−concentrations under the aerobic–anoxic condition.The results showed that NiCu steel tended to be pseudo-passivated in the solutions of 0.05 M NaHCO_(3) and 0.05 M NaHCO_(3)+0.01 M NaCl exposed to air.The cathodic process transformed from oxygen reduction to the common reduction of oxygen andα-FeOOH,while the anodic process was the iron dissolution.As Cl^(−)increased to 0.1 M,the steel tended to be activity dissolution.Due to the blocking effect of rust layer on the oxygen,the cathodic process transformed to the reduction ofα-FeOOH.After the solutions were deoxidized,the cathodic process was controlled by only rust reduction.Meanwhile,both the cathodic process and anodic process of NiCu steel corrosion were significantly inhibited.During the whole aerobic–anoxic immersion,the corrosion rate of NiCu steel increased with Cl^(−)concentration.It was not only related to the promotion of Cl^(−)on the anodic dissolution of steel,but also related to the cathodic reduction of moreα-FeOOH generated,which could accelerate the cathodic process.展开更多
In this study,the pitting corrosion behavior of 13Cr4Ni martensitic stainless steel(BASE)and that modified with rare earth(REM)in 0.1 mol/L Na Cl solution were characterized.Techniques such as automatic secondary elec...In this study,the pitting corrosion behavior of 13Cr4Ni martensitic stainless steel(BASE)and that modified with rare earth(REM)in 0.1 mol/L Na Cl solution were characterized.Techniques such as automatic secondary electron microscope(ASPEX PSEM detector),scanning electron microscope(SEM),transmission electron microscope(TEM),scanning Kelvin probe force microscope(SKP),potentiodynamic and potentiostatic polarizations were employed.The results obtained indicate that BASE steel contains Al_(2)O_(3)/Mn S,Al_(2)O_(3) and Mn S inclusions,while REM steels contain(La,Ce,Cr,Fe)-O and(La,Ce,Cr,Fe)-O-S inclusions.Compared with BASE steel,REM steel is more susceptible to induce the metastable pitting nucleation and repassivation,whereas it restrains the transition from metastable pitting to stable pitting.Adding 0.021%rare earth element to BASE steel can reduce the number and area of inclusions,while that of 0.058%can increase the number and enlarged the size of inclusions,which is also the reason that pitting corrosion resistance of 58 REM steel is slightly lower than that of 21 REM steel.In the process of pitting corrosion induced by Al_(2)O_(3)/Mn S inclusions,Mn S is preferentially anodic dissolved,and also the matrix contacted with Al_(2)O_(3) is subsequently anodic dissolved.For REM steels,anodic dissolution preferentially occurs at the boundary between inclusions and matrix,while(La,Ce,Cr,Fe)-O inclusions chemically dissolve in local acidic environment or are separated from steel matrix.The chemically dissolved substance(La^(3+) and Ce^(3+))of(La,Ce,Cr,Fe)-O inclusions are concentrated in pitting pits,which inhibits its continuous growth.展开更多
The corrosion behavior of mild steel in a simulated coastal atmosphere environment has been investigated by the indoor accelerated wet/dry cyclic corrosion acceleration test(CCT),scanning electron microscopy(SEM),Rama...The corrosion behavior of mild steel in a simulated coastal atmosphere environment has been investigated by the indoor accelerated wet/dry cyclic corrosion acceleration test(CCT),scanning electron microscopy(SEM),Raman spectroscopy and electrochemical measurements.During the CCT test of 60 cycles,the evolution of logarithmic(corrosion rate)vs.logarithmic(CCT cycles)presents a turning point at the 5th cycle,presenting a tendency to increase first and then decrease to gradually stabilize as the CCT cycle prolonged.Before the 5th cycle,γ-FeOOH andβ-FeOOH and Fe_(3)O_(4)were detected,respectively.And then,α-FeOOH as a new chemical composition was detected in the subsequent corrosion cycles.It is found that,after long term corrosion,the rust separated into a relatively dense inner layer rich withα-FeOOH and a loose outer layer rich withγ-FeOOH,both of which have poor electrical conductivity.The rapid increase of corrosion rate in the early stage since reducible corrosion products are involved in the reduction process of the cathode which promotes the dissolution of the anodic metal substrate.Afterward,as the rust layer thickens,the resistance of the rust increases,and the aggressive ions diffusion is blocked,gradually suppressing the electrochemical corrosion process.At last,when the composition and distribution of the rust layer remain stable,the corrosion presents a fluctuating speed around a certain value during the cracking and self-repairing process of the rust layer.展开更多
The effect of tin addition on the atmospheric corrosion behavior of a low-alloy steel in sim ulated coastalindustrial atm osphere has been investigated by indoor wet/dry cyclic corrosion test (CCT). The results indica...The effect of tin addition on the atmospheric corrosion behavior of a low-alloy steel in sim ulated coastalindustrial atm osphere has been investigated by indoor wet/dry cyclic corrosion test (CCT). The results indicate that tin addition can obviously make the steel substrate more resistant to atmospheric corrosion by suppressing the cathodic H^+ reduction reaction, and but tin addition is not of obvious beneficial effect when the steel is covered with a thicker rust layer during long-term corrosion process. The reason lies in the fact that the presence of un-reduced H^+ can lower the electrolyte pH value and lead to a loose and porous rust layer on tin-containing steel sample than that on tin-free steel sample. In addition, the 120 CCT cycles corrosion process of the two steels can be divided into three stages. Both the tin-free and tin-containing steels show an increasing corrosion rate during the initial corrosion stage and then exhibit a decreasing corrosion rate during the second and third corrosion stages. Moreover, tin addition makes the tin-containing steel rust layer have a higher amount of α-FeOOH and lower am ount of γ-FeOOH and Fe3O4 than the tin-free steel rust layer.展开更多
Motivated by the increasing use of Sn-3.0 Ag-0.5 Cu(SAC305)solder in electronics worked in marine atmospheric environment and the uneven distribution of Ag3Sn and Cu6Sn5 intermetallic compounds(IMCs)inβ-Sn matrix,com...Motivated by the increasing use of Sn-3.0 Ag-0.5 Cu(SAC305)solder in electronics worked in marine atmospheric environment and the uneven distribution of Ag3Sn and Cu6Sn5 intermetallic compounds(IMCs)inβ-Sn matrix,comb-like electrodes have been designed for in-situ EIS measurements to study the microstructure induced galvanic corrosion evolution of SAC305 solder in simulated marine atmosphere with high-temperature and high-humidity.Results indicate that in-situ EIS measurement by comb-like electrodes is an effective method for corrosion evolution behavior study of SAC305 solder.Besides,the galvanic effect between Ag3Sn IMCs andβ-Sn matrix can aggravate the corrosion of both as-received and furnace-cooled SAC305 solder as the exposure time proceeds in spite of the presence of corrosion product layer.Pitting corrosion can be preferentially found on furnace-cooled SAC305 with larger Ag3Sn grain size.Moreover,the generated inner stress during phases transformation process with Sn3O(OH)2Cl2 as an intermediate and the possible hydrogen evolution at local acidified sites are supposed to be responsible for the loose,porous,cracked,and non-adherent corrosion product layer.These findings clearly demonstrate the corrosion acceleration behavior and mechanism of SAC305 solder,and provide potential guidelines on maintenance of microelectronic devices for safe operation and longer in-service duration.展开更多
The corrosion kinetics and patina(corrosion products) layer evolution of galvanized steel submitted to wet/dry cyclic corrosion test in a simulated coastal-industrial atmosphere was investigated. The results show that...The corrosion kinetics and patina(corrosion products) layer evolution of galvanized steel submitted to wet/dry cyclic corrosion test in a simulated coastal-industrial atmosphere was investigated. The results show that zinc coating has a greater corrosion rate during the initial period and a lower corrosion rate during the subsequent period, and the patina composition and structure can greatly affect the corrosion kinetics evolution of zinc coating. Moreover, Zn5(OH)6(CO3)2 and Zn4(OH)6 SO4 are identified as the main stable composition and exhibit an increasing relative amount;while Zn12(OH)15Cl3(SO4)3 cannot stably exist and diminish in the patina layer as the corrosion develops.展开更多
The stable operation of electronic devices in marine atmospheric environment is affected by the corrosion deterioration of solder joints,and the effects by atmosphere temperature and chloride deposition are critical.I...The stable operation of electronic devices in marine atmospheric environment is affected by the corrosion deterioration of solder joints,and the effects by atmosphere temperature and chloride deposition are critical.In this work,NaCl deposition and temperature dependent corrosion of Pb-free SAC305 solder in simulated marine atmosphere has been investigated.The results indicate that higher NaCl deposition prolongs the surface wetting time and leads to the final thicker saturated electrolyte film for further corrosion.Higher temperature accelerates the evaporation and contributes to the final thinner saturated NaCl electrolyte film.Besides,the corrosion control process varies under the initially covered thicker NaCl electrolyte layer and under the final saturated much thinner NaCl electrolyte film as the evaporation proceeds.Moreover,the ready oxygen availability through the final thinner saturated NaCl electrolyte film facilitates the formation of corrosion product layer mainly of electrochemically stable SnO2,but higher temperature leads to the final corrosion product layer with smaller crystal size and large cracks.The findings clearly demonstrate the effects of NaCl deposition and temperature on corrosion evolution of SAC305 solder joints and are critical to the daily maintenance of electronic devices for longer service life in marine atmosphere.展开更多
The corrosion behavior of NiCu low alloy steel and Q235 low carbon steel as the candidate materials for geological disposal containers of high-level radioactive waste in the simulated Beishan groundwater was comparati...The corrosion behavior of NiCu low alloy steel and Q235 low carbon steel as the candidate materials for geological disposal containers of high-level radioactive waste in the simulated Beishan groundwater was comparatively studied by weight loss test,electrochemical measurements,scanning electron microscope(SEM),electron probe microanalysis(EPMA),X-ray diffraction(XRD),Raman spectrum and X-ray photoelectron spectroscopy(XPS).The electrochemical results showed that the corrosion potential of NiCu steel and Q235 steel gradually increased with the immersion time.Simultaneously,the cathodic process transited from hydrogen evolution reaction(HER) control to the rust reduction control,while the anodic process was always dominated by the active dissolution of iron.By comparison,both the cathodic resistance and the anodic dissolution resistance of NiCu steel corrosion were apparently higher than that of Q235 steel.The results of rust layer characterization indicated that Ni and Cu elements could be enriched in the inner rust layer of NiCu steel and the rust layer was more compact.As the main corrosion products,the content of α-FeOOH in the rust layer of NiCu steel was obviously increased more than that of Q235 steel.Fe_(6)(OH)_(12)SO_(4)stably existed in the corrosion products of NiCu steel because Ni(Ⅱ) or Cu(Ⅱ)could substitute Fe(Ⅱ) of Fe_(6)(OH)_(12)SO_(4)and increased its oxidation resistance,Moreover,Ni and Cu could also make Fe3O4ionic selective by doping.After the long-term immersion,the corrosion mass loss of NiCu steel was significantly lower than Q235 steel,which further confirmed the benefits of Ni and Cu alloying on improving the steel corrosion resistance.展开更多
The effects of bentonite content on the corrosion behavior of low carbon steel in 5 mM NaHCO3+ 1 mM NaCl + 1 mM Na2SO4 solution were investigated by electrochemical measurements combined with X-ray diffraction(XRD) an...The effects of bentonite content on the corrosion behavior of low carbon steel in 5 mM NaHCO3+ 1 mM NaCl + 1 mM Na2SO4 solution were investigated by electrochemical measurements combined with X-ray diffraction(XRD) and scanning electron microscopy(SEM). In the initial immersion stage, the cathodic process of low carbon steel corrosion was dominated by the reduction of dissolved oxygen, while it transformed to the reduction of ferric corrosion products with the immersion time. The presence of bentonite colloids could suppress the cathodic reduction of oxygen due to their barrier effect on the diffusion of oxygen. However, the barrier performance of bentonite layer was gradually deteriorated due to the coagulation and separation of bentonite colloids caused by the charge neutralization of iron corrosion products dissolved from the steel substrate. More bentonite colloids could maintain the barrier effect for a long time before it was deteriorated by the accumulation of corrosion products. Conversely,it could lose the performance completely, and the corrosion behavior of low carbon steel reverted to the same as that in the blank solution.展开更多
The corrosion evolution of steel disposal container largely depends on the evolution of surrounding bentonite environment in the long-term geological disposal of high-level radioactive wastes. This study focused on th...The corrosion evolution of steel disposal container largely depends on the evolution of surrounding bentonite environment in the long-term geological disposal of high-level radioactive wastes. This study focused on the influence of the deteriorated bentonite sediments on the corrosion behavior of NiCu low alloy steel in the top supernatant and bottom slurry formed by Gaomiaozi bentonite and 0.05 M NaHCO_(3) + 0.1 M NaCl + 0.1 M Na_(2)SO_(4) solution. In the top supernatant, the cathodic process of the steel corrosion was transformed from the reduction in oxygen to the reduction in ferric corrosion products with time as same as that in the blank solution. While in the bottom bentonite slurry, the cathodic process always maintained as the hydrogen evolution reaction due to the coverage of more bentonite sediments. Meanwhile, the corrosion rate of NiCu steel was obviously decreased. In addition, the localized corrosion tendency of the steel could also be reduced by the large amount of deteriorated bentonite sediments.展开更多
基金supported by the National Natural Science Foundation of China(Nos.U1867216,52173304 and 51701222).
文摘The present work focused on investigating the corrosion behavior of NiCu low alloy steel in 0.05 M NaHCO_(3) solutions with different Cl−concentrations under the aerobic–anoxic condition.The results showed that NiCu steel tended to be pseudo-passivated in the solutions of 0.05 M NaHCO_(3) and 0.05 M NaHCO_(3)+0.01 M NaCl exposed to air.The cathodic process transformed from oxygen reduction to the common reduction of oxygen andα-FeOOH,while the anodic process was the iron dissolution.As Cl^(−)increased to 0.1 M,the steel tended to be activity dissolution.Due to the blocking effect of rust layer on the oxygen,the cathodic process transformed to the reduction ofα-FeOOH.After the solutions were deoxidized,the cathodic process was controlled by only rust reduction.Meanwhile,both the cathodic process and anodic process of NiCu steel corrosion were significantly inhibited.During the whole aerobic–anoxic immersion,the corrosion rate of NiCu steel increased with Cl^(−)concentration.It was not only related to the promotion of Cl^(−)on the anodic dissolution of steel,but also related to the cathodic reduction of moreα-FeOOH generated,which could accelerate the cathodic process.
基金supported by the National Natural Science Foundation of China(No.51801219)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2019193)+1 种基金the Scientific Research Project of China Three Gorges Corporation(No.JD-YJ-05006)the National Key Research and Development Program of China(No.2017YFB0702302)。
文摘In this study,the pitting corrosion behavior of 13Cr4Ni martensitic stainless steel(BASE)and that modified with rare earth(REM)in 0.1 mol/L Na Cl solution were characterized.Techniques such as automatic secondary electron microscope(ASPEX PSEM detector),scanning electron microscope(SEM),transmission electron microscope(TEM),scanning Kelvin probe force microscope(SKP),potentiodynamic and potentiostatic polarizations were employed.The results obtained indicate that BASE steel contains Al_(2)O_(3)/Mn S,Al_(2)O_(3) and Mn S inclusions,while REM steels contain(La,Ce,Cr,Fe)-O and(La,Ce,Cr,Fe)-O-S inclusions.Compared with BASE steel,REM steel is more susceptible to induce the metastable pitting nucleation and repassivation,whereas it restrains the transition from metastable pitting to stable pitting.Adding 0.021%rare earth element to BASE steel can reduce the number and area of inclusions,while that of 0.058%can increase the number and enlarged the size of inclusions,which is also the reason that pitting corrosion resistance of 58 REM steel is slightly lower than that of 21 REM steel.In the process of pitting corrosion induced by Al_(2)O_(3)/Mn S inclusions,Mn S is preferentially anodic dissolved,and also the matrix contacted with Al_(2)O_(3) is subsequently anodic dissolved.For REM steels,anodic dissolution preferentially occurs at the boundary between inclusions and matrix,while(La,Ce,Cr,Fe)-O inclusions chemically dissolve in local acidic environment or are separated from steel matrix.The chemically dissolved substance(La^(3+) and Ce^(3+))of(La,Ce,Cr,Fe)-O inclusions are concentrated in pitting pits,which inhibits its continuous growth.
基金financially the Natural Science Foundation of Liaoning Province,China(No.2019JH3/30100037)the National Natural Science Foundation of China(No.51671200)the State Key Laboratory of Metal Material for Marine Equipment and Application(No.SKLMEA-K201907)。
文摘The corrosion behavior of mild steel in a simulated coastal atmosphere environment has been investigated by the indoor accelerated wet/dry cyclic corrosion acceleration test(CCT),scanning electron microscopy(SEM),Raman spectroscopy and electrochemical measurements.During the CCT test of 60 cycles,the evolution of logarithmic(corrosion rate)vs.logarithmic(CCT cycles)presents a turning point at the 5th cycle,presenting a tendency to increase first and then decrease to gradually stabilize as the CCT cycle prolonged.Before the 5th cycle,γ-FeOOH andβ-FeOOH and Fe_(3)O_(4)were detected,respectively.And then,α-FeOOH as a new chemical composition was detected in the subsequent corrosion cycles.It is found that,after long term corrosion,the rust separated into a relatively dense inner layer rich withα-FeOOH and a loose outer layer rich withγ-FeOOH,both of which have poor electrical conductivity.The rapid increase of corrosion rate in the early stage since reducible corrosion products are involved in the reduction process of the cathode which promotes the dissolution of the anodic metal substrate.Afterward,as the rust layer thickens,the resistance of the rust increases,and the aggressive ions diffusion is blocked,gradually suppressing the electrochemical corrosion process.At last,when the composition and distribution of the rust layer remain stable,the corrosion presents a fluctuating speed around a certain value during the cracking and self-repairing process of the rust layer.
基金supported financially by the National Natural Science Fundation of China (Nos. 51501204, 51501201 and 51671200)the National Key Research and Development Program of China (No. 2017YFB0702302)
文摘The effect of tin addition on the atmospheric corrosion behavior of a low-alloy steel in sim ulated coastalindustrial atm osphere has been investigated by indoor wet/dry cyclic corrosion test (CCT). The results indicate that tin addition can obviously make the steel substrate more resistant to atmospheric corrosion by suppressing the cathodic H^+ reduction reaction, and but tin addition is not of obvious beneficial effect when the steel is covered with a thicker rust layer during long-term corrosion process. The reason lies in the fact that the presence of un-reduced H^+ can lower the electrolyte pH value and lead to a loose and porous rust layer on tin-containing steel sample than that on tin-free steel sample. In addition, the 120 CCT cycles corrosion process of the two steels can be divided into three stages. Both the tin-free and tin-containing steels show an increasing corrosion rate during the initial corrosion stage and then exhibit a decreasing corrosion rate during the second and third corrosion stages. Moreover, tin addition makes the tin-containing steel rust layer have a higher amount of α-FeOOH and lower am ount of γ-FeOOH and Fe3O4 than the tin-free steel rust layer.
基金financially supported by the National Natural Science Foundation of China(No.51601057)。
文摘Motivated by the increasing use of Sn-3.0 Ag-0.5 Cu(SAC305)solder in electronics worked in marine atmospheric environment and the uneven distribution of Ag3Sn and Cu6Sn5 intermetallic compounds(IMCs)inβ-Sn matrix,comb-like electrodes have been designed for in-situ EIS measurements to study the microstructure induced galvanic corrosion evolution of SAC305 solder in simulated marine atmosphere with high-temperature and high-humidity.Results indicate that in-situ EIS measurement by comb-like electrodes is an effective method for corrosion evolution behavior study of SAC305 solder.Besides,the galvanic effect between Ag3Sn IMCs andβ-Sn matrix can aggravate the corrosion of both as-received and furnace-cooled SAC305 solder as the exposure time proceeds in spite of the presence of corrosion product layer.Pitting corrosion can be preferentially found on furnace-cooled SAC305 with larger Ag3Sn grain size.Moreover,the generated inner stress during phases transformation process with Sn3O(OH)2Cl2 as an intermediate and the possible hydrogen evolution at local acidified sites are supposed to be responsible for the loose,porous,cracked,and non-adherent corrosion product layer.These findings clearly demonstrate the corrosion acceleration behavior and mechanism of SAC305 solder,and provide potential guidelines on maintenance of microelectronic devices for safe operation and longer in-service duration.
基金supported by the National Natural Science Fundation of China (Nos. 51501204 and 51671200)the Research Program of Corrosion Distribution and Anti-corrosion Measures of Power Transmission in Complex Atmospheric Environment of Large Coastal Cities (No. GZM2014-2-0004)the Science and Technology Department of Henan Province (No. 172102310726)
文摘The corrosion kinetics and patina(corrosion products) layer evolution of galvanized steel submitted to wet/dry cyclic corrosion test in a simulated coastal-industrial atmosphere was investigated. The results show that zinc coating has a greater corrosion rate during the initial period and a lower corrosion rate during the subsequent period, and the patina composition and structure can greatly affect the corrosion kinetics evolution of zinc coating. Moreover, Zn5(OH)6(CO3)2 and Zn4(OH)6 SO4 are identified as the main stable composition and exhibit an increasing relative amount;while Zn12(OH)15Cl3(SO4)3 cannot stably exist and diminish in the patina layer as the corrosion develops.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51601057 and 51701038)and the Marine Science Special Project of Hebei Normal University of Science&Technology(No.2018HY004),and the authors acknowledge the assistance.
文摘The stable operation of electronic devices in marine atmospheric environment is affected by the corrosion deterioration of solder joints,and the effects by atmosphere temperature and chloride deposition are critical.In this work,NaCl deposition and temperature dependent corrosion of Pb-free SAC305 solder in simulated marine atmosphere has been investigated.The results indicate that higher NaCl deposition prolongs the surface wetting time and leads to the final thicker saturated electrolyte film for further corrosion.Higher temperature accelerates the evaporation and contributes to the final thinner saturated NaCl electrolyte film.Besides,the corrosion control process varies under the initially covered thicker NaCl electrolyte layer and under the final saturated much thinner NaCl electrolyte film as the evaporation proceeds.Moreover,the ready oxygen availability through the final thinner saturated NaCl electrolyte film facilitates the formation of corrosion product layer mainly of electrochemically stable SnO2,but higher temperature leads to the final corrosion product layer with smaller crystal size and large cracks.The findings clearly demonstrate the effects of NaCl deposition and temperature on corrosion evolution of SAC305 solder joints and are critical to the daily maintenance of electronic devices for longer service life in marine atmosphere.
基金supported by the National Natural Science Foundation of China (Nos.U1867216,52173304 and 51701222)。
文摘The corrosion behavior of NiCu low alloy steel and Q235 low carbon steel as the candidate materials for geological disposal containers of high-level radioactive waste in the simulated Beishan groundwater was comparatively studied by weight loss test,electrochemical measurements,scanning electron microscope(SEM),electron probe microanalysis(EPMA),X-ray diffraction(XRD),Raman spectrum and X-ray photoelectron spectroscopy(XPS).The electrochemical results showed that the corrosion potential of NiCu steel and Q235 steel gradually increased with the immersion time.Simultaneously,the cathodic process transited from hydrogen evolution reaction(HER) control to the rust reduction control,while the anodic process was always dominated by the active dissolution of iron.By comparison,both the cathodic resistance and the anodic dissolution resistance of NiCu steel corrosion were apparently higher than that of Q235 steel.The results of rust layer characterization indicated that Ni and Cu elements could be enriched in the inner rust layer of NiCu steel and the rust layer was more compact.As the main corrosion products,the content of α-FeOOH in the rust layer of NiCu steel was obviously increased more than that of Q235 steel.Fe_(6)(OH)_(12)SO_(4)stably existed in the corrosion products of NiCu steel because Ni(Ⅱ) or Cu(Ⅱ)could substitute Fe(Ⅱ) of Fe_(6)(OH)_(12)SO_(4)and increased its oxidation resistance,Moreover,Ni and Cu could also make Fe3O4ionic selective by doping.After the long-term immersion,the corrosion mass loss of NiCu steel was significantly lower than Q235 steel,which further confirmed the benefits of Ni and Cu alloying on improving the steel corrosion resistance.
基金financially supported by the National Natural Science Foundation of China (Nos. 51701222, U1867216 and 51471175)。
文摘The effects of bentonite content on the corrosion behavior of low carbon steel in 5 mM NaHCO3+ 1 mM NaCl + 1 mM Na2SO4 solution were investigated by electrochemical measurements combined with X-ray diffraction(XRD) and scanning electron microscopy(SEM). In the initial immersion stage, the cathodic process of low carbon steel corrosion was dominated by the reduction of dissolved oxygen, while it transformed to the reduction of ferric corrosion products with the immersion time. The presence of bentonite colloids could suppress the cathodic reduction of oxygen due to their barrier effect on the diffusion of oxygen. However, the barrier performance of bentonite layer was gradually deteriorated due to the coagulation and separation of bentonite colloids caused by the charge neutralization of iron corrosion products dissolved from the steel substrate. More bentonite colloids could maintain the barrier effect for a long time before it was deteriorated by the accumulation of corrosion products. Conversely,it could lose the performance completely, and the corrosion behavior of low carbon steel reverted to the same as that in the blank solution.
基金financially supported by the National Natural Science Foundation of China(Nos.U1867216,51701222 and 51471175)。
文摘The corrosion evolution of steel disposal container largely depends on the evolution of surrounding bentonite environment in the long-term geological disposal of high-level radioactive wastes. This study focused on the influence of the deteriorated bentonite sediments on the corrosion behavior of NiCu low alloy steel in the top supernatant and bottom slurry formed by Gaomiaozi bentonite and 0.05 M NaHCO_(3) + 0.1 M NaCl + 0.1 M Na_(2)SO_(4) solution. In the top supernatant, the cathodic process of the steel corrosion was transformed from the reduction in oxygen to the reduction in ferric corrosion products with time as same as that in the blank solution. While in the bottom bentonite slurry, the cathodic process always maintained as the hydrogen evolution reaction due to the coverage of more bentonite sediments. Meanwhile, the corrosion rate of NiCu steel was obviously decreased. In addition, the localized corrosion tendency of the steel could also be reduced by the large amount of deteriorated bentonite sediments.