Although considerable research has been conducted on nitrate reduction by zero-valent iron powder （Fe^0）, these studies were mostly operated under anaerobic conditions with invariable pH that was unsuitable for prac...Although considerable research has been conducted on nitrate reduction by zero-valent iron powder （Fe^0）, these studies were mostly operated under anaerobic conditions with invariable pH that was unsuitable for practical application. Without reaction conditions （dissolved oxygen or reaction pH） control, this work aimed at subjecting the kinetics of denitrification by microscale Fe^0 （160-200 mesh） to analysis the factors affecting the denitrification of nitrate and the composition of iron reductive products coating upon the iron surface. Results of the kinetics study have indicated that a higher initial concentration of nitrate would yield a greater reaction rate constant. The reduction rate of nitrate increased with increasing Fe^0 dosage. The reaction can be described as a pseudo-first order reaction with respect to nitrate concentration or Fe^0 dosage. Experimental results also suggested that nitrate reduction by microscale Fe^0 without reaction condition control primarily was an acid-driven surface-mediated process, and the reaction order was 0.65 with respect to hydrogen ion concentration. The analyses of X-ray diffractometry and X-ray photoelectron spectroscopy indicated that a black coating, consisted of Fe2O3, Fe3O4 and FeO（OH）, was formed on the surface of iron grains as an iron corrosion product when the system initial pH was lower than 5. The proportion of FeO（OH） increased as reaction time went on, whereas the proportion of Fe3O4 decreased.展开更多
The effects of alternating magnetic field on the corrosion morphologies, corrosion rate, and corrosion products of copper in 3.5% NaCl solution, sea water, and magnetized sea water were investigated using electrochemi...The effects of alternating magnetic field on the corrosion morphologies, corrosion rate, and corrosion products of copper in 3.5% NaCl solution, sea water, and magnetized sea water were investigated using electrochemical test, scanning electron microscopy/energy dispersive analysis system of X-ray （SEM/EDAX）, and X-ray diffraction （XRD）. The results show that the corrosion rate of copper in magnetized sea water is minimal. Moreover, the surface of the specimen in magnetized sea water is uniform and compact as compared with those in 3.5% NaCl solution and sea water. The corrosion products of copper in magnetized sea water are mainly Cu2O and CuCl2. However, the corrosion products in sea water are CuCl, Cu2Cl（OH）3, and FeCl3-6H2O. The electrochemical corrosion mechanisms of copper in the three media were also discussed.展开更多
Open-circuit potential measurements and Raman spectroscopy were used to investigate the reverse crevice corrosion phenomenon and its corresponding corrosion products. With the aid of these techniques, the existence of...Open-circuit potential measurements and Raman spectroscopy were used to investigate the reverse crevice corrosion phenomenon and its corresponding corrosion products. With the aid of these techniques, the existence of reverse-crevice corrosion in copper was verified, i.e., while the surface of a crevice was corrosion free, the outside surface of the copper was attacked. The processes associated with this phe-nomenon were classified into three phases, and different compositions of the corrosion products were determined. Raman spectra showed that copper and Cu2O were found in the crevice, while CuO, Cu2O, and CuCl2 were the corrosion products on the bold surface. Based on these findings, a hypothesis relating to the three phases of reverse crevice corrosion has been proposed.展开更多
The effect of cooling liquid used for heat exchangers on the Cu alloy corrosion products has been examined using potential-time measurements under applied current condition (anodizing), potentiodynamic polarization, X...The effect of cooling liquid used for heat exchangers on the Cu alloy corrosion products has been examined using potential-time measurements under applied current condition (anodizing), potentiodynamic polarization, X-ray diffraction (XRD) and infrared spectroscopy (IR) The corrosion products formed on the Cu alloy surface during anodizing, are Cu2O, Cu2(OH)3Cl, and Cu2S. NaCl is detected in the corrosion products. The film formation depends on the applied current and the shift of potential to nobler direction indicates its formation progress.展开更多
Corrosion product formed on zinc sample during 2 weeks immersion in saline solution has been investigated.The corrosion layer morphology as well as its chemical composition,was analyzed using scanning electron microsc...Corrosion product formed on zinc sample during 2 weeks immersion in saline solution has been investigated.The corrosion layer morphology as well as its chemical composition,was analyzed using scanning electron microscopy(SEM),x-ray diffraction(XRD),x-ray photoelectron spectroscopy(XPS)and Fourier transform infrared spectroscopy(FTIR).Electrochemical measurement was used to analyze the corrosion behavior.Zinc oxide,zinc hydroxide and zinc hydroxide chloride were formed on zinc surface in saline solution.The thickness of corrosion layer increased with the time increased.The pure Zn has an estimated corrosion rate of 0.063mmy^−1 after immersion for 336 h.Probable mechanisms of zinc corrosion products formation are presented.展开更多
The effect of in-situ local damage of uniform porous corrosion products on the localised corrosion of carbon steel is investigated using the wire beam electrode technique(WBE)combined with morphology characterisation ...The effect of in-situ local damage of uniform porous corrosion products on the localised corrosion of carbon steel is investigated using the wire beam electrode technique(WBE)combined with morphology characterisation and electrochemical tests.The WBE measurements demonstrate that the localised corrosion is enhanced by the in-situ local removal of porous corrosion products,supported by the morphology characterisation and electrochemical tests.The enhanced localised corrosion does not originate from the damaged wire in WBE where the corrosion products are removed but from the other undamaged wires,which is reported for the first time.A mechanism is proposed that the intensive anodic polarisation effect of the damaged wire on the undamaged wires could account for the enhanced localised corrosion,which is due to the protective corrosion products newly formed on the damaged surface and the increase in the potential of damaged wire.展开更多
A numerical study is reported of laminar natural convective heat and mass transfer on a vertical cooled plate for water containing metal corrosion products at super-critical pressures. The influence of variable proper...A numerical study is reported of laminar natural convective heat and mass transfer on a vertical cooled plate for water containing metal corrosion products at super-critical pressures. The influence of variable properties at super-critical pressures on natural convection has been analyzed. The difference between heat and mass transfer under cooling or heating conditions is also discussed and some correlations for heat and mass transfer under cooling conditions are recommended.展开更多
The formation and development of corrosion products on carbon steel surface during the initial stage of atmospheric corrosion in a laboratory simulated environment have been studied by scanning electron microscopy （...The formation and development of corrosion products on carbon steel surface during the initial stage of atmospheric corrosion in a laboratory simulated environment have been studied by scanning electron microscopy （SEM） and Raman spectroscopy. The results showed that two different shapes of corrosion products, that is, ring and chain, were formed in the initial stage of corrosion. MnS clusters were found in the nuclei of corrosion products at the active local corrosion sites. The ring-shaped products were composed of lepidocrocite （γ-FeOOH） and maghemite （γ-Fe2O2 ） transformed from lepidocrocite. The chain-type products were goethite （α-FeOOH）. A formation mechanism of the corrosion products is proposed.展开更多
Atmospheric corrosion of aluminum alloy 2024 （AA2024） with salt lake water was simulated through a laboratory- accelerated test of cyclic wet-dry and electrochemical techniques. Effects of the soluble magnesium salt...Atmospheric corrosion of aluminum alloy 2024 （AA2024） with salt lake water was simulated through a laboratory- accelerated test of cyclic wet-dry and electrochemical techniques. Effects of the soluble magnesium salt contained in the salt water were investigated by scanning electron microscope （SEM）, transmission electron microscope （TEM）, energy dispersive spectrometer （EDS）, electron probe micro analyzer （EPMA）, X-ray diffraction （XRD）, infrared transmission spectroscope （IR）, and atmospheric corrosion monitor （ACM）. The results showed that, with the deposition, atmospheric corrosion of AA2024 could occur when the relative humidity （RH） was lower than 30%. A main crystalline component of corrosion products, layered double hydroxides （LDH）, [Mg1-xAlx（OH）2]^x＋ Clx-·mH2O （LDH-C1）, was determined, which meant that magnesium ion played an important role in the corrosion process. It not only facilitated the corrosion as a result of deliquescence, but also was involved in the corrosion process as a reactant.展开更多
The corrosion mechanism of Mg-Y alloys in 3.5% NaCl solution was investigated by electrochemical testing and SEM observation. The electrochemical results indicated that the corrosion potential of Mg-Y alloys in 3.5% N...The corrosion mechanism of Mg-Y alloys in 3.5% NaCl solution was investigated by electrochemical testing and SEM observation. The electrochemical results indicated that the corrosion potential of Mg-Y alloys in 3.5% NaCl solution increased with the increase of Y addition. The corrosion rate increased with the increase of Y addition because of the increase of Mg24Y5 intermetallic amounts. The corrosion gradually deteriorated with the increase of immersion time. The corrosion morphologies of the alloys were general corrosion for Mg-0.25Y and pitting corrosion for Mg-8Y and Mg-15Y, respectively. The main solid corrosion products were Mg（OH）2 and Mg2（OH）3C1·4H2O.展开更多
A novel calculation model is proposed aiming at the problem of concrete cover cracking induced by reinforcement corrosion. In this article, the relationship between the corrosion depth of the bar and the thickness of ...A novel calculation model is proposed aiming at the problem of concrete cover cracking induced by reinforcement corrosion. In this article, the relationship between the corrosion depth of the bar and the thickness of the rust layer is established. By deducing the radial displacement expression of concrete, the formula for corrosion depth and corrosion pressure before cracking is proposed. The crack depth of cover in accordance with the maximum corrosion pressure is deduced; furthermore, the corrosion depth and corrosion pressure at the cracking time are obtained. Finally, the theoretical model is validated by several experiments, and the calculated values agree well with the experiment results.展开更多
The atmospheric corrosion behavior of new-type weathering steels(WSs)was comparatively studied,and the effects of Nb and Sb during corrosion were clarified in detail through field exposure and characterization.The res...The atmospheric corrosion behavior of new-type weathering steels(WSs)was comparatively studied,and the effects of Nb and Sb during corrosion were clarified in detail through field exposure and characterization.The results showed that the addition of Nb and Sb played positive roles in corrosion resistance,but there was a clear difference between these two elements.Nb addition slightly improved the rust property of conventional WS but could not inhibit the electrochemical process.In contrast,Sb addition significantly improved the corrosion resistance from the aspects of electrochemistry and rust layer.Compared with only 0.06wt%Nb,the combination of 0.05wt%Sb and 0.06wt%Nb could better optimize the rust structure,accelerate the formation of a high proportion of dense and protectiveα-FeOOH,repel the invasion of Cl^(−),and retard the localized acidification at the bottom of the pit.展开更多
The corrosion behavior of 16Mn steel was studied in saturated H2S or H2S/CO2 solutions containing different Cl^-concentrations at 80℃.The microstructure and chemical composition of the corrosion products were investi...The corrosion behavior of 16Mn steel was studied in saturated H2S or H2S/CO2 solutions containing different Cl^-concentrations at 80℃.The microstructure and chemical composition of the corrosion products were investigated through scanning electron microscopy,energy-dispersive X-ray spectroscopy,EPMA,and X-ray diffraction.Results showed that the corrosion rate decreased with increasing Cl^-concentration in saturated H2S or H2S/CO2 solution at pH 4.Conversely,the corrosion rate increased with increasing Cl^-concentration in saturated H2S solution at pH 6.The relative H^＋concentration decreased because of the increase of Cl^-concentration at pH 4,and Cl^-acted as a catalyst in the corrosive medium at pH 6 because the net H^＋concentration decreased obviously compared with the condition at pH4.Cl^-promoted the formation of Fe-deficient iron sulfide at pH 4,and the opposite effect was observed in the nearly neutral solution.The corrosion rate increased firstly with increasing Cl^-concentration and then decreased in the saturated H2S/CO2solution at pH 6.The corrosion products were mainly composed of two kinds of iron sulfide.Sulfide FeS（1-x） was a kind of tetragonal crystal,whereas the other was the hexagonal/monoclinic iron sulfide Fe（1-x）S.The corrosion film that was mainly composed of FeS（1-x） did not confer a protective effect on the base metal.The atomic ratio of Fe/S was more than 1 for FeS（1-x）.The appearance of sulfide FeS（1-x） resembled a square block or small,needlelike,flocculent particles.The atomic ratio of Fe/S was less than 1 for Fe（1-x）S,and the corrosion film mainly composed of Fe（1-x）S conferred some protective property on the base metal.The sulfide FeS（1-x） exhibited a long claviform morphology with a hexagonal or quadrilateral cross-sectional shape.展开更多
In this paper,the thermo-hydro-mechanical(THM)response of claystone is studied via a series of parametric studies,considering the evolution of mechanical properties and deformation behavior of corroded steel.The numer...In this paper,the thermo-hydro-mechanical(THM)response of claystone is studied via a series of parametric studies,considering the evolution of mechanical properties and deformation behavior of corroded steel.The numerical simulations are performed by using a coupled THM finite element code and two different constitutive models:a visco-elastoplastic model for geological formation and a von Mises type model for steel liner.The mechanical properties and deformation behavior of corroded steel are described in a conceptual model.Finally,a disposal tunnel supported by a steel liner is studied and a series of parametric studies is defined to demonstrate the corrosion effects of steel liner on the THM response of the claystone.The comparison of different numerical calculations exhibits that the volumetric expansion related to corrosion products has an important impact on the stress and displacement fields in the claystone surrounding the disposal tunnel.However,the evolutions of temperature and liquid pressure in the claystone are essentially controlled by its THM properties and independent of the steel corrosion.展开更多
The corrosion degradation behavior of a Mg-Ca alloy with high Ca content aiming for a potential bone repair material in the simulated body fluid（SBF） was investigated.The microstructure and phase constitution of the...The corrosion degradation behavior of a Mg-Ca alloy with high Ca content aiming for a potential bone repair material in the simulated body fluid（SBF） was investigated.The microstructure and phase constitution of the pristine Mg-30%Ca（mass fraction） alloy were characterized with scanning electron microscopy（SEM） and X-ray diffraction（XRD）.The Mg-30%Ca alloy samples were immersed in the SBF for 90 d,and the morphology,composition and cytotoxicity of the final corrosion product were examined.It is found that Mg-30%Ca alloy is composed of α-Mg and Mg2 Ca phases.During the corrosion process in the SBF,the Mg2 Ca phase acts as an anode and the α-Mg phase acts as a cathode.The final corrosion product of the Mg-30%Ca alloy in SBF includes a small amount of black precipitates and white suspended particles.The white suspended particles are Mg（OH）2 and the black particles are believed to have a core-shell structure.The cytotoxicity experiments indicate that these black precipitates do not induce toxicity to cells.展开更多
The initial corrosion behavior of pure zinc in a simulated tropical marine atmosphere was investigated using gravimetric method,scanning electron microscope combined with energy dispersive spectroscopy(SEM-EDS),X-ray ...The initial corrosion behavior of pure zinc in a simulated tropical marine atmosphere was investigated using gravimetric method,scanning electron microscope combined with energy dispersive spectroscopy(SEM-EDS),X-ray diffractometry(XRD),Fourier transform infrared spectrometry(FTIR)and electrochemical impedance spectroscopy(EIS).The kinetics of corrosion process is a decelerating process following the empirical equation D=At^n(n<1).The protectiveness of the corrosion product layer could be attributed to the formation of simonkolleite,Zn5(OH)8Cl2·H2O,which could inhibit the rate determining step,namely charge transfer step,of the electrochemical corrosion process.A model of the evolution process of the product layers formed on zinc was proposed.In addition,the regularity of the corrosion rate of zinc as a function of the NaCl deposition rate can be described by a power function.展开更多
To investigate the correlation between structure characteristics and wear resistance of CO2 corrosion product scales at high temperature and high pressure, an autoclave was used to prepare CO2 corrosion product scales...To investigate the correlation between structure characteristics and wear resistance of CO2 corrosion product scales at high temperature and high pressure, an autoclave was used to prepare CO2 corrosion product scales on N80 steel in carbon dioxide corrosion environment. The correlation between wear resistance of the scales and many other factors, such as temperature, pressure, morphology, structure, velocity of fluid medium, sand grain size, and so on, was comparatively analyzed by a self assembled wear device, and the scale morphologies before or after being worn were observed by scanning electron microscope （SEM）. And then the surface grain size and thickness of scale were measured. The results showed that the cross-section of the corrosion scale was of a double-layer structure, the outer layer of which was composed of regular crystals, whereas the inner layer was a thin scale of fine grains. The outer grain size and thickness of scale varied with temperature, and the initial wear loss was consistent with the surface grain size; at the same time, the total wear loss corresponded to the thickness of scale. Compared to wear resist- ance in different depths of the scale, it was found that the structure of scale was a double-layer structure in cross-section, and the wear resistance of inner layer was better than that of the outer layer; the closer the scale to the matrix, the greater was the wear resistance of scale; and the larger the size or the higher the rotary speed of solid grain in multiphase flowing medium, the more was the wear loss of scale.展开更多
For high corrosion resistance and extensively modified biodegradable Mg-based alloys and composites for bone implants,a new Mgbased matrix model prepared by powder metallurgy is discussed and developed.In this researc...For high corrosion resistance and extensively modified biodegradable Mg-based alloys and composites for bone implants,a new Mgbased matrix model prepared by powder metallurgy is discussed and developed.In this research,Mg-5 wt.%Zn alloys were selected as a case.And they were impacted by hot extrusion and aging treatments to construct microstructure with different characteristics.Their selfforming corrosion product layer in Ringer’s solution,biodegradable behavior and corrosion mechanism were minutely investigated by in vitro degradation,electrochemical corrosion and cytocompatibility.The results demonstrated the extruded Mg-5 wt.%Zn alloy aged for 96 h showed high corrosion resistance,good biocompatibility for L929 and excellent ability of maintaining sample integrity during the immersion.Significantly,the alloy showed fine-grain microstructure and uniform distributed hundred nano-sized second phases,which promoted the formation of the uniform and smooth corrosion product layer at the beginning of immersion.The corrosion product layer was more stable in chloride containing aqueous solution and could be directly formed and repaired quickly,which effectively protected the matrix from further corrosion.In addition,an ideal model of Mg-based matrix for bone tissue engineering was tried to presume and propose by discussing the causal relationship between microstructure and bio-corrosion process.展开更多
A novel Cu?6.5Ni?1Al?1Si?0.15Mg?0.15Ce alloy with super-high strength was designed and its corrosion behavior in3.5%NaCl solution at25°C was investigated by the means of SEM observation,TEM observation and XPS an...A novel Cu?6.5Ni?1Al?1Si?0.15Mg?0.15Ce alloy with super-high strength was designed and its corrosion behavior in3.5%NaCl solution at25°C was investigated by the means of SEM observation,TEM observation and XPS analysis.The alloy after solution treatment,80%cold rolling and aging at450°C for1h had the best comprehensive properties with hardness of HV314,electrical conductivity of19.4%IACS,tensile strength of1017MPa,and average annual corrosion rate of0.028mm/a.The oxides and chloride products formed at first,followed by the formation of dyroxides products.The alloy showed super-high strength,good electrical conductivity and corrosion resistant because Ni2Si hindered the precipitation of large NiAl at the grain boundary and the denickelefication of the alloy.展开更多
The anisotropic deposit film formed during the galvanic corrosion can impede the mass transfer of the involved species,thereby affecting the electro-chemical behavior and the evolution of galvanic corrosion.The limita...The anisotropic deposit film formed during the galvanic corrosion can impede the mass transfer of the involved species,thereby affecting the electro-chemical behavior and the evolution of galvanic corrosion.The limitations of experimental studies in the spatial-temporal scales restrict a deeper understanding of the corrosion mechanism,which can be complemented by numerical simulation.A multi-physics coupled model is proposed in this work to systematically investigate the temporal and spatial evolution of galvanic corrosion of the Mg-steel couple with the growing anisotropic deposition layer.By utilizing the multi-physics field coupled technique,various coupled physical-chemical processes underlying the corrosion behavior are built into the model,including chemical reactions,ionic mass transfer in the bulk solution and the deposition layer,interfacial reaction,deposition of corrosion products as well as the morphological transitions caused by metal dissolution and deposition.In particular,the anisotropic deposit film is considered to be a porous layer with a porosity varying in time and space as the corrosion evolves.The predicted corrosion morphology by this model is better than the previous models.The coupled relationship between the electrochemical behavior(e.g.,electrode reaction kinetics,current density,surface potential)and the physical processes(e.g.,ionic transport,geometric evolution of metal surface and film interface)is revealed.The results indicate that a porous deposition layer with a denser inner layer and a loose outer layer is generated,leading to more significant inhibition of mass transfer in the inner layer than the outer layer.The anisotropism of the deposition layer results in a non-uniform conductivity distribution and a discontinuous current density distribution in the electrolyte.The current density on the electrode surface is inhibited by the deposition layer and the variation in the cathode/anode area ratio during the corrosion process.The competition between the transport process and the electrochemical reaction determines the spatial-temporal evolution of the ion concentration.展开更多
基金supported by the Development Program for Outstanding Young Teachers in Harbin Institute of Technology (No. HITQNJS. 2007. 038)
文摘Although considerable research has been conducted on nitrate reduction by zero-valent iron powder （Fe^0）, these studies were mostly operated under anaerobic conditions with invariable pH that was unsuitable for practical application. Without reaction conditions （dissolved oxygen or reaction pH） control, this work aimed at subjecting the kinetics of denitrification by microscale Fe^0 （160-200 mesh） to analysis the factors affecting the denitrification of nitrate and the composition of iron reductive products coating upon the iron surface. Results of the kinetics study have indicated that a higher initial concentration of nitrate would yield a greater reaction rate constant. The reduction rate of nitrate increased with increasing Fe^0 dosage. The reaction can be described as a pseudo-first order reaction with respect to nitrate concentration or Fe^0 dosage. Experimental results also suggested that nitrate reduction by microscale Fe^0 without reaction condition control primarily was an acid-driven surface-mediated process, and the reaction order was 0.65 with respect to hydrogen ion concentration. The analyses of X-ray diffractometry and X-ray photoelectron spectroscopy indicated that a black coating, consisted of Fe2O3, Fe3O4 and FeO（OH）, was formed on the surface of iron grains as an iron corrosion product when the system initial pH was lower than 5. The proportion of FeO（OH） increased as reaction time went on, whereas the proportion of Fe3O4 decreased.
文摘The effects of alternating magnetic field on the corrosion morphologies, corrosion rate, and corrosion products of copper in 3.5% NaCl solution, sea water, and magnetized sea water were investigated using electrochemical test, scanning electron microscopy/energy dispersive analysis system of X-ray （SEM/EDAX）, and X-ray diffraction （XRD）. The results show that the corrosion rate of copper in magnetized sea water is minimal. Moreover, the surface of the specimen in magnetized sea water is uniform and compact as compared with those in 3.5% NaCl solution and sea water. The corrosion products of copper in magnetized sea water are mainly Cu2O and CuCl2. However, the corrosion products in sea water are CuCl, Cu2Cl（OH）3, and FeCl3-6H2O. The electrochemical corrosion mechanisms of copper in the three media were also discussed.
文摘Open-circuit potential measurements and Raman spectroscopy were used to investigate the reverse crevice corrosion phenomenon and its corresponding corrosion products. With the aid of these techniques, the existence of reverse-crevice corrosion in copper was verified, i.e., while the surface of a crevice was corrosion free, the outside surface of the copper was attacked. The processes associated with this phe-nomenon were classified into three phases, and different compositions of the corrosion products were determined. Raman spectra showed that copper and Cu2O were found in the crevice, while CuO, Cu2O, and CuCl2 were the corrosion products on the bold surface. Based on these findings, a hypothesis relating to the three phases of reverse crevice corrosion has been proposed.
文摘The effect of cooling liquid used for heat exchangers on the Cu alloy corrosion products has been examined using potential-time measurements under applied current condition (anodizing), potentiodynamic polarization, X-ray diffraction (XRD) and infrared spectroscopy (IR) The corrosion products formed on the Cu alloy surface during anodizing, are Cu2O, Cu2(OH)3Cl, and Cu2S. NaCl is detected in the corrosion products. The film formation depends on the applied current and the shift of potential to nobler direction indicates its formation progress.
基金the National Key R&D Program of China(Grant No.2016YFC1102500)National Natural Science Foundation of China(Grant No.51503014 and No.51501008)financial support from the State Key Laboratory for Advanced Metals and Materials(No.2016Z-03).
文摘Corrosion product formed on zinc sample during 2 weeks immersion in saline solution has been investigated.The corrosion layer morphology as well as its chemical composition,was analyzed using scanning electron microscopy(SEM),x-ray diffraction(XRD),x-ray photoelectron spectroscopy(XPS)and Fourier transform infrared spectroscopy(FTIR).Electrochemical measurement was used to analyze the corrosion behavior.Zinc oxide,zinc hydroxide and zinc hydroxide chloride were formed on zinc surface in saline solution.The thickness of corrosion layer increased with the time increased.The pure Zn has an estimated corrosion rate of 0.063mmy^−1 after immersion for 336 h.Probable mechanisms of zinc corrosion products formation are presented.
基金the Opening Project of Material Corrosion and Protection Key Laboratory of Sichuan Province(No.2017CL18)。
文摘The effect of in-situ local damage of uniform porous corrosion products on the localised corrosion of carbon steel is investigated using the wire beam electrode technique(WBE)combined with morphology characterisation and electrochemical tests.The WBE measurements demonstrate that the localised corrosion is enhanced by the in-situ local removal of porous corrosion products,supported by the morphology characterisation and electrochemical tests.The enhanced localised corrosion does not originate from the damaged wire in WBE where the corrosion products are removed but from the other undamaged wires,which is reported for the first time.A mechanism is proposed that the intensive anodic polarisation effect of the damaged wire on the undamaged wires could account for the enhanced localised corrosion,which is due to the protective corrosion products newly formed on the damaged surface and the increase in the potential of damaged wire.
文摘A numerical study is reported of laminar natural convective heat and mass transfer on a vertical cooled plate for water containing metal corrosion products at super-critical pressures. The influence of variable properties at super-critical pressures on natural convection has been analyzed. The difference between heat and mass transfer under cooling or heating conditions is also discussed and some correlations for heat and mass transfer under cooling conditions are recommended.
基金National Natural Science Foundation of China (50499331-8)Ministry of Science and Technology of China(2004DKA10080)
文摘The formation and development of corrosion products on carbon steel surface during the initial stage of atmospheric corrosion in a laboratory simulated environment have been studied by scanning electron microscopy （SEM） and Raman spectroscopy. The results showed that two different shapes of corrosion products, that is, ring and chain, were formed in the initial stage of corrosion. MnS clusters were found in the nuclei of corrosion products at the active local corrosion sites. The ring-shaped products were composed of lepidocrocite （γ-FeOOH） and maghemite （γ-Fe2O2 ） transformed from lepidocrocite. The chain-type products were goethite （α-FeOOH）. A formation mechanism of the corrosion products is proposed.
基金Project(51131007) supported by the National Natural Science Foundation of China
文摘Atmospheric corrosion of aluminum alloy 2024 （AA2024） with salt lake water was simulated through a laboratory- accelerated test of cyclic wet-dry and electrochemical techniques. Effects of the soluble magnesium salt contained in the salt water were investigated by scanning electron microscope （SEM）, transmission electron microscope （TEM）, energy dispersive spectrometer （EDS）, electron probe micro analyzer （EPMA）, X-ray diffraction （XRD）, infrared transmission spectroscope （IR）, and atmospheric corrosion monitor （ACM）. The results showed that, with the deposition, atmospheric corrosion of AA2024 could occur when the relative humidity （RH） was lower than 30%. A main crystalline component of corrosion products, layered double hydroxides （LDH）, [Mg1-xAlx（OH）2]^x＋ Clx-·mH2O （LDH-C1）, was determined, which meant that magnesium ion played an important role in the corrosion process. It not only facilitated the corrosion as a result of deliquescence, but also was involved in the corrosion process as a reactant.
基金Project(2011BAE22B01)supported by the National Key Technology R&D Program of Chinasupported by Beijing Engineering Research Center for Advanced Manufacturing and Evaluation of Special Vehicle Parts which is jointly built by Beijing North Vehicle Group Corporation and University of Science and Technology Beijing
文摘The corrosion mechanism of Mg-Y alloys in 3.5% NaCl solution was investigated by electrochemical testing and SEM observation. The electrochemical results indicated that the corrosion potential of Mg-Y alloys in 3.5% NaCl solution increased with the increase of Y addition. The corrosion rate increased with the increase of Y addition because of the increase of Mg24Y5 intermetallic amounts. The corrosion gradually deteriorated with the increase of immersion time. The corrosion morphologies of the alloys were general corrosion for Mg-0.25Y and pitting corrosion for Mg-8Y and Mg-15Y, respectively. The main solid corrosion products were Mg（OH）2 and Mg2（OH）3C1·4H2O.
基金This paper is supported by the National Natural Science Foundation of China (Nos. 50278039, 50538070)
文摘A novel calculation model is proposed aiming at the problem of concrete cover cracking induced by reinforcement corrosion. In this article, the relationship between the corrosion depth of the bar and the thickness of the rust layer is established. By deducing the radial displacement expression of concrete, the formula for corrosion depth and corrosion pressure before cracking is proposed. The crack depth of cover in accordance with the maximum corrosion pressure is deduced; furthermore, the corrosion depth and corrosion pressure at the cracking time are obtained. Finally, the theoretical model is validated by several experiments, and the calculated values agree well with the experiment results.
基金financially supported by the National Natural Science Foundation of China (No. 52101068)the China Postdoctoral Science Foundation (No. 2022M710348)
文摘The atmospheric corrosion behavior of new-type weathering steels(WSs)was comparatively studied,and the effects of Nb and Sb during corrosion were clarified in detail through field exposure and characterization.The results showed that the addition of Nb and Sb played positive roles in corrosion resistance,but there was a clear difference between these two elements.Nb addition slightly improved the rust property of conventional WS but could not inhibit the electrochemical process.In contrast,Sb addition significantly improved the corrosion resistance from the aspects of electrochemistry and rust layer.Compared with only 0.06wt%Nb,the combination of 0.05wt%Sb and 0.06wt%Nb could better optimize the rust structure,accelerate the formation of a high proportion of dense and protectiveα-FeOOH,repel the invasion of Cl^(−),and retard the localized acidification at the bottom of the pit.
基金Funded by National Natural Science Foundation of China(No.51765035)
文摘The corrosion behavior of 16Mn steel was studied in saturated H2S or H2S/CO2 solutions containing different Cl^-concentrations at 80℃.The microstructure and chemical composition of the corrosion products were investigated through scanning electron microscopy,energy-dispersive X-ray spectroscopy,EPMA,and X-ray diffraction.Results showed that the corrosion rate decreased with increasing Cl^-concentration in saturated H2S or H2S/CO2 solution at pH 4.Conversely,the corrosion rate increased with increasing Cl^-concentration in saturated H2S solution at pH 6.The relative H^＋concentration decreased because of the increase of Cl^-concentration at pH 4,and Cl^-acted as a catalyst in the corrosive medium at pH 6 because the net H^＋concentration decreased obviously compared with the condition at pH4.Cl^-promoted the formation of Fe-deficient iron sulfide at pH 4,and the opposite effect was observed in the nearly neutral solution.The corrosion rate increased firstly with increasing Cl^-concentration and then decreased in the saturated H2S/CO2solution at pH 6.The corrosion products were mainly composed of two kinds of iron sulfide.Sulfide FeS（1-x） was a kind of tetragonal crystal,whereas the other was the hexagonal/monoclinic iron sulfide Fe（1-x）S.The corrosion film that was mainly composed of FeS（1-x） did not confer a protective effect on the base metal.The atomic ratio of Fe/S was more than 1 for FeS（1-x）.The appearance of sulfide FeS（1-x） resembled a square block or small,needlelike,flocculent particles.The atomic ratio of Fe/S was less than 1 for Fe（1-x）S,and the corrosion film mainly composed of Fe（1-x）S conferred some protective property on the base metal.The sulfide FeS（1-x） exhibited a long claviform morphology with a hexagonal or quadrilateral cross-sectional shape.
基金supported by the National Natural Science Foundation of China (NSFC) (Grant No. 51609081)
文摘In this paper,the thermo-hydro-mechanical(THM)response of claystone is studied via a series of parametric studies,considering the evolution of mechanical properties and deformation behavior of corroded steel.The numerical simulations are performed by using a coupled THM finite element code and two different constitutive models:a visco-elastoplastic model for geological formation and a von Mises type model for steel liner.The mechanical properties and deformation behavior of corroded steel are described in a conceptual model.Finally,a disposal tunnel supported by a steel liner is studied and a series of parametric studies is defined to demonstrate the corrosion effects of steel liner on the THM response of the claystone.The comparison of different numerical calculations exhibits that the volumetric expansion related to corrosion products has an important impact on the stress and displacement fields in the claystone surrounding the disposal tunnel.However,the evolutions of temperature and liquid pressure in the claystone are essentially controlled by its THM properties and independent of the steel corrosion.
基金Project(51271131)supported by the National Natural Science Foundation of China
文摘The corrosion degradation behavior of a Mg-Ca alloy with high Ca content aiming for a potential bone repair material in the simulated body fluid（SBF） was investigated.The microstructure and phase constitution of the pristine Mg-30%Ca（mass fraction） alloy were characterized with scanning electron microscopy（SEM） and X-ray diffraction（XRD）.The Mg-30%Ca alloy samples were immersed in the SBF for 90 d,and the morphology,composition and cytotoxicity of the final corrosion product were examined.It is found that Mg-30%Ca alloy is composed of α-Mg and Mg2 Ca phases.During the corrosion process in the SBF,the Mg2 Ca phase acts as an anode and the α-Mg phase acts as a cathode.The final corrosion product of the Mg-30%Ca alloy in SBF includes a small amount of black precipitates and white suspended particles.The white suspended particles are Mg（OH）2 and the black particles are believed to have a core-shell structure.The cytotoxicity experiments indicate that these black precipitates do not induce toxicity to cells.
基金Project (201604046014) supported by Guangzhou Industry-University-Research Collaborative Innovation Alliance Special Program,ChinaProjects (51671197,51601199) supported by the National Natural Science Foundation of China
文摘The initial corrosion behavior of pure zinc in a simulated tropical marine atmosphere was investigated using gravimetric method,scanning electron microscope combined with energy dispersive spectroscopy(SEM-EDS),X-ray diffractometry(XRD),Fourier transform infrared spectrometry(FTIR)and electrochemical impedance spectroscopy(EIS).The kinetics of corrosion process is a decelerating process following the empirical equation D=At^n(n<1).The protectiveness of the corrosion product layer could be attributed to the formation of simonkolleite,Zn5(OH)8Cl2·H2O,which could inhibit the rate determining step,namely charge transfer step,of the electrochemical corrosion process.A model of the evolution process of the product layers formed on zinc was proposed.In addition,the regularity of the corrosion rate of zinc as a function of the NaCl deposition rate can be described by a power function.
基金Item Sponsored by National Natural Science Foundation of China (50231020) , National Basic Research Programof China(G1999065004) ,2001'Key Laboratory Opening Fund of Corrosion and Protection of Tabular Goods Research Center of ChinaNational Petroleum Corporation (ZYT-01070)
文摘To investigate the correlation between structure characteristics and wear resistance of CO2 corrosion product scales at high temperature and high pressure, an autoclave was used to prepare CO2 corrosion product scales on N80 steel in carbon dioxide corrosion environment. The correlation between wear resistance of the scales and many other factors, such as temperature, pressure, morphology, structure, velocity of fluid medium, sand grain size, and so on, was comparatively analyzed by a self assembled wear device, and the scale morphologies before or after being worn were observed by scanning electron microscope （SEM）. And then the surface grain size and thickness of scale were measured. The results showed that the cross-section of the corrosion scale was of a double-layer structure, the outer layer of which was composed of regular crystals, whereas the inner layer was a thin scale of fine grains. The outer grain size and thickness of scale varied with temperature, and the initial wear loss was consistent with the surface grain size; at the same time, the total wear loss corresponded to the thickness of scale. Compared to wear resist- ance in different depths of the scale, it was found that the structure of scale was a double-layer structure in cross-section, and the wear resistance of inner layer was better than that of the outer layer; the closer the scale to the matrix, the greater was the wear resistance of scale; and the larger the size or the higher the rotary speed of solid grain in multiphase flowing medium, the more was the wear loss of scale.
基金The authors acknowledge the Project(81472058)sup-ported by the National Natural Science Foundation of Chinathe financial support of the 2015 ShanDong province project of outstanding subject talent group.the project(LSD-KB1806)+2 种基金supported by the foundation of National Key labo-ratory of Shock Wave and Detonation Physics and the project(11802284)supported by the National Natural Science Foun-dation of China.The project(2017GK2120)supported by the Key Research and Development Program of Hunan Province and the Natural Science Foundation of Hunan Province of China(2018JJ2506).
文摘For high corrosion resistance and extensively modified biodegradable Mg-based alloys and composites for bone implants,a new Mgbased matrix model prepared by powder metallurgy is discussed and developed.In this research,Mg-5 wt.%Zn alloys were selected as a case.And they were impacted by hot extrusion and aging treatments to construct microstructure with different characteristics.Their selfforming corrosion product layer in Ringer’s solution,biodegradable behavior and corrosion mechanism were minutely investigated by in vitro degradation,electrochemical corrosion and cytocompatibility.The results demonstrated the extruded Mg-5 wt.%Zn alloy aged for 96 h showed high corrosion resistance,good biocompatibility for L929 and excellent ability of maintaining sample integrity during the immersion.Significantly,the alloy showed fine-grain microstructure and uniform distributed hundred nano-sized second phases,which promoted the formation of the uniform and smooth corrosion product layer at the beginning of immersion.The corrosion product layer was more stable in chloride containing aqueous solution and could be directly formed and repaired quickly,which effectively protected the matrix from further corrosion.In addition,an ideal model of Mg-based matrix for bone tissue engineering was tried to presume and propose by discussing the causal relationship between microstructure and bio-corrosion process.
基金Project(51271203)supported by the National Natural Science Foundation of China
文摘A novel Cu?6.5Ni?1Al?1Si?0.15Mg?0.15Ce alloy with super-high strength was designed and its corrosion behavior in3.5%NaCl solution at25°C was investigated by the means of SEM observation,TEM observation and XPS analysis.The alloy after solution treatment,80%cold rolling and aging at450°C for1h had the best comprehensive properties with hardness of HV314,electrical conductivity of19.4%IACS,tensile strength of1017MPa,and average annual corrosion rate of0.028mm/a.The oxides and chloride products formed at first,followed by the formation of dyroxides products.The alloy showed super-high strength,good electrical conductivity and corrosion resistant because Ni2Si hindered the precipitation of large NiAl at the grain boundary and the denickelefication of the alloy.
基金supported by the National Natural Science Foundation of China(Grant no.51906200)the Key Project of National Natural Science Foundation of China(Grant no.51839010)+2 种基金the Key Laboratory Foundation of Education Department of Shaanxi(Grant no.19JS045)the China Postdoctoral Science Foundation(No.2019TQ0248No.2019M663735)。
文摘The anisotropic deposit film formed during the galvanic corrosion can impede the mass transfer of the involved species,thereby affecting the electro-chemical behavior and the evolution of galvanic corrosion.The limitations of experimental studies in the spatial-temporal scales restrict a deeper understanding of the corrosion mechanism,which can be complemented by numerical simulation.A multi-physics coupled model is proposed in this work to systematically investigate the temporal and spatial evolution of galvanic corrosion of the Mg-steel couple with the growing anisotropic deposition layer.By utilizing the multi-physics field coupled technique,various coupled physical-chemical processes underlying the corrosion behavior are built into the model,including chemical reactions,ionic mass transfer in the bulk solution and the deposition layer,interfacial reaction,deposition of corrosion products as well as the morphological transitions caused by metal dissolution and deposition.In particular,the anisotropic deposit film is considered to be a porous layer with a porosity varying in time and space as the corrosion evolves.The predicted corrosion morphology by this model is better than the previous models.The coupled relationship between the electrochemical behavior(e.g.,electrode reaction kinetics,current density,surface potential)and the physical processes(e.g.,ionic transport,geometric evolution of metal surface and film interface)is revealed.The results indicate that a porous deposition layer with a denser inner layer and a loose outer layer is generated,leading to more significant inhibition of mass transfer in the inner layer than the outer layer.The anisotropism of the deposition layer results in a non-uniform conductivity distribution and a discontinuous current density distribution in the electrolyte.The current density on the electrode surface is inhibited by the deposition layer and the variation in the cathode/anode area ratio during the corrosion process.The competition between the transport process and the electrochemical reaction determines the spatial-temporal evolution of the ion concentration.
