A low-energy plasma electrolytic oxidation(LePEO)technique is developed to simultaneously improve energy efficiency and anti-corrosion.Ionic liquids(1-butyl-3-methylimidazole tetrafluoroborate(BmimBF_(4)))as sustainab...A low-energy plasma electrolytic oxidation(LePEO)technique is developed to simultaneously improve energy efficiency and anti-corrosion.Ionic liquids(1-butyl-3-methylimidazole tetrafluoroborate(BmimBF_(4)))as sustainable corrosion inhibitors are chosen to investigate the corrosion inhibition behavior of ionic liquid(ILs)during the LePEO process for LA91 magnesium-lithium(Mg-Li)alloy.Results show that the ionic liquid BmimBF_(4)participates in the LePEO coating formation process,causing an increment in coating thickness and surface roughness.The low conductivity of the ionic liquid is responsible for the voltage and breakdown voltage increases during the LePEO with IL process(LePEO-IL).After adding BmimBF_(4),corrosion current density decreases from 1.159×10^(−4)A·cm^(−2)to 8.143×10^(−6)A·cm^(−2).The impedance modulus increases to 1.048×10^(4)Ω·cm^(−2)and neutral salt spray remains intact for 24 h.The superior corrosion resistance of the LePEO coating assisted by ionic liquid could be mainly attributed to its compact and thick barrier layer and physical absorption of ionic liquid.The ionic liquid-assisted LePEO technique provides a promising approach to reducing energy consumption and improving film performance.展开更多
In this study,the interactions between a Ga-based liquid metal,GaInSn,and several metal materials,including pure metals(Ni and Ti)and alloys(316H stainless steel(SS)and GH3535),at 650℃were investigated.The aim was to...In this study,the interactions between a Ga-based liquid metal,GaInSn,and several metal materials,including pure metals(Ni and Ti)and alloys(316H stainless steel(SS)and GH3535),at 650℃were investigated.The aim was to evaluate the corrosion performance and select a suitable candidate material for use as a molten salt manometer diaphragm in thermal energy storage systems.The results indicated that the alloys(316H SS and GH3535)exhibited less corrosion than pure metals(Ni and Ti)in liquid GaInSn.Ga-rich binary intermetallic compounds were found to form on the surfaces of all the tested metal materials exposed to liquid GaInSn,as a result of the decomposition of liquid GaInSn and its reaction with the constituent elements of the metal materials.The corrosion mechanism for all the tested materials exposed to liquid GaInSn was also investigated and proposed,which may aid in selecting the optimal candidate material when liquid GaInSn is used as the pressure-sensing medium.展开更多
As one of candidates for the fuel cladding or structure material used in fourth generation fission and fusiondemonstrate reactor, MAX phase has the properties of both ceramic and metal, such as high melting point, hig...As one of candidates for the fuel cladding or structure material used in fourth generation fission and fusiondemonstrate reactor, MAX phase has the properties of both ceramic and metal, such as high melting point, hightemperaturestability, good erosion resistance and radiation-damage tolerance[1;2]. Max phase is a series of ceramicsof nanolamellar and hexagonal structure. M represents transition element. A represents the third or fourth maingroup element. X represent N and C. In the design of lead-cooled fast reactor, it is required that the materialshould endure the corrosion of liquid Pb-Bi alloy. Therefore, understanding of the oxide layers and their growthmechanisms in LBE is fundamentally important for the development of candidate materials.展开更多
Two kinds of materials, soluble and insoluble in liquid zinc, such as Fe and FeB, are separately dealt with.A new theory is presented for insoluble materials. Based on the theory, the surface defects of insoluble mate...Two kinds of materials, soluble and insoluble in liquid zinc, such as Fe and FeB, are separately dealt with.A new theory is presented for insoluble materials. Based on the theory, the surface defects of insoluble materials are themain reason that the matcrials are correded.展开更多
The isothermal corrosion testing, microscopic examination and the performance of Fe3Si alloy as materials of construction for bath hardware in continuous hot-dipping lines were studied. The corrosion of Fe3Si alloy in...The isothermal corrosion testing, microscopic examination and the performance of Fe3Si alloy as materials of construction for bath hardware in continuous hot-dipping lines were studied. The corrosion of Fe3Si alloy in molten zinc was controlled by attacking the grain boundaries preferentially. Aluminum reacted with iron of Fe3Si alloy firstly while the samples were immersed in molten zinc, although aluminum contents in the molten zinc were very low. The phase of reaction product was thought to be Fe2Al5. The corrosion rate of the Fe3Si alloy in molten zinc was determined to be approximately 2.9×10^-3 mm/h, therefore the liquid zinc corrosion resistance of Fe3Si alloy was very weak.展开更多
Electrochemical measurement, optical microscopy, and scanning electron microscopy were employed to investigate the corrosion behavior of some low alloy steels. The steels were held under a thin liquid film of 0.5wt% N...Electrochemical measurement, optical microscopy, and scanning electron microscopy were employed to investigate the corrosion behavior of some low alloy steels. The steels were held under a thin liquid film of 0.5wt% NaCl aqueous solution. It is found that the steels with the same chemical composition but different micmstructures exhibit obviously different corrosion behaviors. However, the corrosion behavior of the steels with different compositions but the same microstructnres may be similar in the present investigation. The corrosion rate of bainite is slower than that of ferrite and pearlite. The corrosion products of bainite are uniform and fine. The size of carbon-rich phases produces a great impact on the corrosion of the steels, whether in the initial stage or in the long tenn. It is easy to induce large pitting for carbon-rich phases with large size, which damages the compactness of the rust layer.展开更多
Four protic ionic liquids(ILs)were synthesized via a one-step method by using benzotriazole(BTA)and benzimidazole as cations,and benzenesulfonic acid and 2-naphthalenesulfonic acid(NSA)as anions.These ILs were used as...Four protic ionic liquids(ILs)were synthesized via a one-step method by using benzotriazole(BTA)and benzimidazole as cations,and benzenesulfonic acid and 2-naphthalenesulfonic acid(NSA)as anions.These ILs were used as green corrosion inhibitors for brass specimens in a nitric acid solution.The structure of the protic ILs was characterized by 1H-NMR,13C-NMR,and FT-IR spectroscopy.The effects of the IL structure,IL concentration,acid concentration,and corrosion time on the surface morphology of brass specimens and the inhibition efficiency(η%)of ILs were investigated by the weight loss method combined with SEM and EDS spectroscopy.Polarization curves and impedance spectroscopy were used to analyze the electrochemical corrosion inhibition mechanism of ILs.Results showed that IL synthesis was a proton transfer process,and the proton of the–SO3H group on NSA was deprived by BTA.IL[BTA][NSA],which had a high charge density and large conjugateπband,was the most effective inhibitor for brass corrosion.Theη%of[BTA][NSA]decreased with the increase in acid concentration and corrosion time,which showed an increment with the increase in[BTA][NSA]concentration.The higher theη%of[BTA][NSA]is,the smoother the surface of the brass specimens is,and the smaller the undistributed area of Cu element will be.Corrosion inhibiting mechanism from electrochemical analysis indicated that the addition of[BTA][NSA]increased the polarization resistance of the brass electrode significantly and suppressed both anodic and cathodic reactions.展开更多
Corrosion behavior of four oxide dispersion strengthened(ODS) ferritic alloys exposed in thermal convective liquid sodium loop for 4 000 h was examined.Surface observation results reveal that coral-like surfaces with ...Corrosion behavior of four oxide dispersion strengthened(ODS) ferritic alloys exposed in thermal convective liquid sodium loop for 4 000 h was examined.Surface observation results reveal that coral-like surfaces with deposit initially formed on surfaces of all exposed specimens.In tested alloy S2,χ-phase precipitated in specimen center,and a depleted χ- phase zone formed near the specimen surface.There is a transition area between the surface and center.In the other tested alloys,no notable change on microstructure was observed.Grain boundary attack was not found in any of the tested specimens.Tensile test results indicate that sodium corrosion of the four ODS ferritic alloys for 3 000 h had no notable effect on their tensile properties.展开更多
The corrosion behavior(in chloride medium) of the surface layer of SSM-HPDC plates of alloys 7075-T6 and 2024-T6 was compared with that of the wrought alloys 7075-T6 and 2024-T6.Potentiodynamic testing was performed i...The corrosion behavior(in chloride medium) of the surface layer of SSM-HPDC plates of alloys 7075-T6 and 2024-T6 was compared with that of the wrought alloys 7075-T6 and 2024-T6.Potentiodynamic testing was performed in deaerated 3.5%NaCl solution.In separate tests,the open-circuit potential was monitored in aerated 3.5% NaCl for 30 min after immersion.The electrochemical tests show that there is no significant difference in the pitting potential of the wrought alloys and that of the Cu-enriched surfaces of the SSM-HPDC alloys.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
In this study, corrosion inhibiting properties of amino pentadecylphenols (APPs) derived from Cashew Nut Shell Liquid (CNSL) on mild steel in aerated 0.10 M HCl at 303 K were studied using Electrochemical Impedance Sp...In this study, corrosion inhibiting properties of amino pentadecylphenols (APPs) derived from Cashew Nut Shell Liquid (CNSL) on mild steel in aerated 0.10 M HCl at 303 K were studied using Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization measurements. Both methods indicated the potential of a mixture of amino pentadecyphenols to serve as a corrosion inhibitor in mild steel in 0.10 M HCl. Corrosion inhibition efficiencies were observed to increase with increase in the inhibitor concentration, with maximum corrosion inhibition of about 98% at inhibitor concentration of 600 ppm. The adsorption of the inhibitor on mild steel surface was found to obey Temkin adsorption isotherm, signifying physical adsorption of the inhibitor molecules on mild steel surface.展开更多
In order to have a better understanding on the corrosion mechanisms of bulk two-phase Ag-25Cu (at.%) alloys with different microstructures, two bulk nanocrystalline Ag-25Cu alloys and one coarse grained counterpart we...In order to have a better understanding on the corrosion mechanisms of bulk two-phase Ag-25Cu (at.%) alloys with different microstructures, two bulk nanocrystalline Ag-25Cu alloys and one coarse grained counterpart were prepared by liquid phase reduction (LPR), mechanical alloying (MA) and powder metallurgy (PM) methods, respectively. Their corrosion behavior was investigated comparatively using electrochemical methods in NaCl aqueous solution. Results show that the microstructure of the coarse grained PMAg-25Cu alloy is extremely inhomogeneous. On the contrary, compared with PMAg-25Cu alloy, the microstructures of the nanocrystalline LPRAg-25Cu and MAAg-25Cu alloys are more homogeneous, especially for LPRAg-25Cu alloy. The corrosion rate of MAAg-25Cu alloy is higher than that of PMAg-25Cu alloy, but lower than that of LPRAg-25Cu alloy. Furthermore, the passive films formed by three Ag-25Cu alloys exhibit n-type semiconducting properties. The passive current density of LPRAg-25Cu alloy is lower than that of PMAg-25Cu alloy, but higher that of MAAg-25Cu alloy.展开更多
An orifice is used widely as a flow meter or a contraction device in pipeline systems in hydro-power plants, thermal power plants, and chemical plants because of its simple construction, high reliability, and low cost...An orifice is used widely as a flow meter or a contraction device in pipeline systems in hydro-power plants, thermal power plants, and chemical plants because of its simple construction, high reliability, and low cost. However, it is well known that flow-accelerated corrosion (FAC) occurs on the pipe wall downstream of the orifice. Some of the authors have examined FAC through experimental and numerical analyses and have reported that one of the major governing parameters of FAC for single-phase water flow is the pressure fluctuation p’ on the pipe wall, and also that pipe wall thinning rate TR can be estimated by p’. In addition, they have presented the effects of the ori-fice geometry on p’ or TR, and have described a method for suppressing p’ or TR. In the present study, FAC for a two-phase air-water bubble flow is examined and compared with the single-phase water flow experimentally. Further, it is shown that because p’ is also considered a governing parameter of FAC for a two-phase air-water bubble flow, TR can be estimated using p’. It is also indicated that, by using a downstream pipe with a smaller diameter than that of the upstream pipe, p’ or TR can be suppressed.展开更多
Aluminum was electrodeposited with constant current on AZ31 magnesium alloy pretreated under optimized conditions from trimethyl-phenyl-ammonium chloride and anhydrous aluminum chloride （TMPAC-AlCl3） quaternary ammo...Aluminum was electrodeposited with constant current on AZ31 magnesium alloy pretreated under optimized conditions from trimethyl-phenyl-ammonium chloride and anhydrous aluminum chloride （TMPAC-AlCl3） quaternary ammonium room temperature ionic liquids with benzene as a co-solvent. The corrosion resistance of the as-deposited Al layers was evaluated in 3.5% NaCl solution by the electrochemical technologies. The Al depositions were characterized by scanning electron microscopy equipped with energy dispersion X-ray. The results show that the microstructures of the Al depositions have spherical equiaxed grains obtained at a high current density, and bulk grains at a low current density. The Al deposition obtained at 12.3 mA/cm2 has a smooth and compact surface. The electrochemical measurements indicate that the thicker Al deposition can more effectively protect the Mg substrate. The Al deposition with bulk grains hardly protects the AZ31 Mg substrate from corrosion owing to its porosity.展开更多
Laser surface melting（LSM） is a high-energy surface treatment that allows modification of the microstructure and surface properties of Mg alloys. In the present work, an attempt of LSM on magnesium alloy with liquid...Laser surface melting（LSM） is a high-energy surface treatment that allows modification of the microstructure and surface properties of Mg alloys. In the present work, an attempt of LSM on magnesium alloy with liquid nitrogen-assisted cooling（LNSC） was carried out to get the higher cooling rate and improve the surface properties. The experimental results were compared with those of Ar gas protection at room temperature. The samples after LSM with LNSC resulted in a thinner melted layer, a highly homogeneous, refined melted microstructure and formed a lot of worm-like nanocrystals and local amorphous structures. Microhardness of the melted layer with LNAC was improved to HV 90-148 as compared to HV 65-105 of the samples with Ar gas protection. The corrosion resistance of the melted layer in a 3.5% Na Cl solution（mass fraction） was improved because of the grain refinement and redistribution of β-Mg17Al12 phases following rapid quenching associated with the process.展开更多
基金supported by the Natural Science Founda-tion of Beijing(Grant No.2182017,2202017).
文摘A low-energy plasma electrolytic oxidation(LePEO)technique is developed to simultaneously improve energy efficiency and anti-corrosion.Ionic liquids(1-butyl-3-methylimidazole tetrafluoroborate(BmimBF_(4)))as sustainable corrosion inhibitors are chosen to investigate the corrosion inhibition behavior of ionic liquid(ILs)during the LePEO process for LA91 magnesium-lithium(Mg-Li)alloy.Results show that the ionic liquid BmimBF_(4)participates in the LePEO coating formation process,causing an increment in coating thickness and surface roughness.The low conductivity of the ionic liquid is responsible for the voltage and breakdown voltage increases during the LePEO with IL process(LePEO-IL).After adding BmimBF_(4),corrosion current density decreases from 1.159×10^(−4)A·cm^(−2)to 8.143×10^(−6)A·cm^(−2).The impedance modulus increases to 1.048×10^(4)Ω·cm^(−2)and neutral salt spray remains intact for 24 h.The superior corrosion resistance of the LePEO coating assisted by ionic liquid could be mainly attributed to its compact and thick barrier layer and physical absorption of ionic liquid.The ionic liquid-assisted LePEO technique provides a promising approach to reducing energy consumption and improving film performance.
基金supported by the National Natural Science Foundation of China(Nos.12005289 and 52071331)the National Key R&D Program of China(No.2019YFA0210000)the State Key Laboratory of Nuclear Detection and Electronics,University of Science and Technology of China(No.SKLPDE-KF-202316)。
文摘In this study,the interactions between a Ga-based liquid metal,GaInSn,and several metal materials,including pure metals(Ni and Ti)and alloys(316H stainless steel(SS)and GH3535),at 650℃were investigated.The aim was to evaluate the corrosion performance and select a suitable candidate material for use as a molten salt manometer diaphragm in thermal energy storage systems.The results indicated that the alloys(316H SS and GH3535)exhibited less corrosion than pure metals(Ni and Ti)in liquid GaInSn.Ga-rich binary intermetallic compounds were found to form on the surfaces of all the tested metal materials exposed to liquid GaInSn,as a result of the decomposition of liquid GaInSn and its reaction with the constituent elements of the metal materials.The corrosion mechanism for all the tested materials exposed to liquid GaInSn was also investigated and proposed,which may aid in selecting the optimal candidate material when liquid GaInSn is used as the pressure-sensing medium.
文摘As one of candidates for the fuel cladding or structure material used in fourth generation fission and fusiondemonstrate reactor, MAX phase has the properties of both ceramic and metal, such as high melting point, hightemperaturestability, good erosion resistance and radiation-damage tolerance[1;2]. Max phase is a series of ceramicsof nanolamellar and hexagonal structure. M represents transition element. A represents the third or fourth maingroup element. X represent N and C. In the design of lead-cooled fast reactor, it is required that the materialshould endure the corrosion of liquid Pb-Bi alloy. Therefore, understanding of the oxide layers and their growthmechanisms in LBE is fundamentally important for the development of candidate materials.
文摘Two kinds of materials, soluble and insoluble in liquid zinc, such as Fe and FeB, are separately dealt with.A new theory is presented for insoluble materials. Based on the theory, the surface defects of insoluble materials are themain reason that the matcrials are correded.
基金This work was financially supported by the National Natural Science Foundation of China (No.50274005).
文摘The isothermal corrosion testing, microscopic examination and the performance of Fe3Si alloy as materials of construction for bath hardware in continuous hot-dipping lines were studied. The corrosion of Fe3Si alloy in molten zinc was controlled by attacking the grain boundaries preferentially. Aluminum reacted with iron of Fe3Si alloy firstly while the samples were immersed in molten zinc, although aluminum contents in the molten zinc were very low. The phase of reaction product was thought to be Fe2Al5. The corrosion rate of the Fe3Si alloy in molten zinc was determined to be approximately 2.9×10^-3 mm/h, therefore the liquid zinc corrosion resistance of Fe3Si alloy was very weak.
基金supported by the Major State Basic Research and Development Program of China (No.2004CB619102)
文摘Electrochemical measurement, optical microscopy, and scanning electron microscopy were employed to investigate the corrosion behavior of some low alloy steels. The steels were held under a thin liquid film of 0.5wt% NaCl aqueous solution. It is found that the steels with the same chemical composition but different micmstructures exhibit obviously different corrosion behaviors. However, the corrosion behavior of the steels with different compositions but the same microstructnres may be similar in the present investigation. The corrosion rate of bainite is slower than that of ferrite and pearlite. The corrosion products of bainite are uniform and fine. The size of carbon-rich phases produces a great impact on the corrosion of the steels, whether in the initial stage or in the long tenn. It is easy to induce large pitting for carbon-rich phases with large size, which damages the compactness of the rust layer.
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(grant no.21802047)and the Scientific Research Funds of Huaqiao University(grant no.600005-Z17Y0073),Xiamen,China.
文摘Four protic ionic liquids(ILs)were synthesized via a one-step method by using benzotriazole(BTA)and benzimidazole as cations,and benzenesulfonic acid and 2-naphthalenesulfonic acid(NSA)as anions.These ILs were used as green corrosion inhibitors for brass specimens in a nitric acid solution.The structure of the protic ILs was characterized by 1H-NMR,13C-NMR,and FT-IR spectroscopy.The effects of the IL structure,IL concentration,acid concentration,and corrosion time on the surface morphology of brass specimens and the inhibition efficiency(η%)of ILs were investigated by the weight loss method combined with SEM and EDS spectroscopy.Polarization curves and impedance spectroscopy were used to analyze the electrochemical corrosion inhibition mechanism of ILs.Results showed that IL synthesis was a proton transfer process,and the proton of the–SO3H group on NSA was deprived by BTA.IL[BTA][NSA],which had a high charge density and large conjugateπband,was the most effective inhibitor for brass corrosion.Theη%of[BTA][NSA]decreased with the increase in acid concentration and corrosion time,which showed an increment with the increase in[BTA][NSA]concentration.The higher theη%of[BTA][NSA]is,the smoother the surface of the brass specimens is,and the smaller the undistributed area of Cu element will be.Corrosion inhibiting mechanism from electrochemical analysis indicated that the addition of[BTA][NSA]increased the polarization resistance of the brass electrode significantly and suppressed both anodic and cathodic reactions.
文摘Corrosion behavior of four oxide dispersion strengthened(ODS) ferritic alloys exposed in thermal convective liquid sodium loop for 4 000 h was examined.Surface observation results reveal that coral-like surfaces with deposit initially formed on surfaces of all exposed specimens.In tested alloy S2,χ-phase precipitated in specimen center,and a depleted χ- phase zone formed near the specimen surface.There is a transition area between the surface and center.In the other tested alloys,no notable change on microstructure was observed.Grain boundary attack was not found in any of the tested specimens.Tensile test results indicate that sodium corrosion of the four ODS ferritic alloys for 3 000 h had no notable effect on their tensile properties.
文摘The corrosion behavior(in chloride medium) of the surface layer of SSM-HPDC plates of alloys 7075-T6 and 2024-T6 was compared with that of the wrought alloys 7075-T6 and 2024-T6.Potentiodynamic testing was performed in deaerated 3.5%NaCl solution.In separate tests,the open-circuit potential was monitored in aerated 3.5% NaCl for 30 min after immersion.The electrochemical tests show that there is no significant difference in the pitting potential of the wrought alloys and that of the Cu-enriched surfaces of the SSM-HPDC alloys.
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.
文摘In this study, corrosion inhibiting properties of amino pentadecylphenols (APPs) derived from Cashew Nut Shell Liquid (CNSL) on mild steel in aerated 0.10 M HCl at 303 K were studied using Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization measurements. Both methods indicated the potential of a mixture of amino pentadecyphenols to serve as a corrosion inhibitor in mild steel in 0.10 M HCl. Corrosion inhibition efficiencies were observed to increase with increase in the inhibitor concentration, with maximum corrosion inhibition of about 98% at inhibitor concentration of 600 ppm. The adsorption of the inhibitor on mild steel surface was found to obey Temkin adsorption isotherm, signifying physical adsorption of the inhibitor molecules on mild steel surface.
基金Projects(51271127,51501118)supported by the National Natural Science Foundation of ChinaProject(2018304025)supported by Liaoning Provincial Key Research and Development Program,ChinaProject(201602679)supported by the Natural Science Foundation of Liaoning Province,China
文摘In order to have a better understanding on the corrosion mechanisms of bulk two-phase Ag-25Cu (at.%) alloys with different microstructures, two bulk nanocrystalline Ag-25Cu alloys and one coarse grained counterpart were prepared by liquid phase reduction (LPR), mechanical alloying (MA) and powder metallurgy (PM) methods, respectively. Their corrosion behavior was investigated comparatively using electrochemical methods in NaCl aqueous solution. Results show that the microstructure of the coarse grained PMAg-25Cu alloy is extremely inhomogeneous. On the contrary, compared with PMAg-25Cu alloy, the microstructures of the nanocrystalline LPRAg-25Cu and MAAg-25Cu alloys are more homogeneous, especially for LPRAg-25Cu alloy. The corrosion rate of MAAg-25Cu alloy is higher than that of PMAg-25Cu alloy, but lower than that of LPRAg-25Cu alloy. Furthermore, the passive films formed by three Ag-25Cu alloys exhibit n-type semiconducting properties. The passive current density of LPRAg-25Cu alloy is lower than that of PMAg-25Cu alloy, but higher that of MAAg-25Cu alloy.
文摘An orifice is used widely as a flow meter or a contraction device in pipeline systems in hydro-power plants, thermal power plants, and chemical plants because of its simple construction, high reliability, and low cost. However, it is well known that flow-accelerated corrosion (FAC) occurs on the pipe wall downstream of the orifice. Some of the authors have examined FAC through experimental and numerical analyses and have reported that one of the major governing parameters of FAC for single-phase water flow is the pressure fluctuation p’ on the pipe wall, and also that pipe wall thinning rate TR can be estimated by p’. In addition, they have presented the effects of the ori-fice geometry on p’ or TR, and have described a method for suppressing p’ or TR. In the present study, FAC for a two-phase air-water bubble flow is examined and compared with the single-phase water flow experimentally. Further, it is shown that because p’ is also considered a governing parameter of FAC for a two-phase air-water bubble flow, TR can be estimated using p’. It is also indicated that, by using a downstream pipe with a smaller diameter than that of the upstream pipe, p’ or TR can be suppressed.
文摘Aluminum was electrodeposited with constant current on AZ31 magnesium alloy pretreated under optimized conditions from trimethyl-phenyl-ammonium chloride and anhydrous aluminum chloride （TMPAC-AlCl3） quaternary ammonium room temperature ionic liquids with benzene as a co-solvent. The corrosion resistance of the as-deposited Al layers was evaluated in 3.5% NaCl solution by the electrochemical technologies. The Al depositions were characterized by scanning electron microscopy equipped with energy dispersion X-ray. The results show that the microstructures of the Al depositions have spherical equiaxed grains obtained at a high current density, and bulk grains at a low current density. The Al deposition obtained at 12.3 mA/cm2 has a smooth and compact surface. The electrochemical measurements indicate that the thicker Al deposition can more effectively protect the Mg substrate. The Al deposition with bulk grains hardly protects the AZ31 Mg substrate from corrosion owing to its porosity.
基金Project(51305292)supported by the National Natural Science Foundation of ChinaProject(2014-024)supported by Shanxi Scholarship Council of China
文摘Laser surface melting（LSM） is a high-energy surface treatment that allows modification of the microstructure and surface properties of Mg alloys. In the present work, an attempt of LSM on magnesium alloy with liquid nitrogen-assisted cooling（LNSC） was carried out to get the higher cooling rate and improve the surface properties. The experimental results were compared with those of Ar gas protection at room temperature. The samples after LSM with LNSC resulted in a thinner melted layer, a highly homogeneous, refined melted microstructure and formed a lot of worm-like nanocrystals and local amorphous structures. Microhardness of the melted layer with LNAC was improved to HV 90-148 as compared to HV 65-105 of the samples with Ar gas protection. The corrosion resistance of the melted layer in a 3.5% Na Cl solution（mass fraction） was improved because of the grain refinement and redistribution of β-Mg17Al12 phases following rapid quenching associated with the process.
