The polarization curves of mild steel in de-aerated 0.5 mol NaHCO 3+0.5 mol Na 2CO 3 solution with and without erodent particles of 300 g/L of 100 μm alumina have been measured using a rotating cylinder electrode (RC...The polarization curves of mild steel in de-aerated 0.5 mol NaHCO 3+0.5 mol Na 2CO 3 solution with and without erodent particles of 300 g/L of 100 μm alumina have been measured using a rotating cylinder electrode (RCE) apparatus over the range of rotation speeds from 0 to 4 000 r/min. The results show that the mild steel in the de-aerated slurry exhibits classical active/passive polarization behavior. The speed of cylinder rotation has a great effect in the presence of particles on the active dissolution current density. The erosion-corrosion process is severely erosion-dominated for the mild steel. However, the poor corrosion resistance of the mild steel in such turbulent slurries is also significant, especially at lower than 4 m/s.展开更多
Proton Exchange Membrane Water Electrolyzers(PEMWE)are efficient and sustainable hydrogen production devices.This article analyzes their static and dynamic electrical models integrated with degradation mechanisms.Stat...Proton Exchange Membrane Water Electrolyzers(PEMWE)are efficient and sustainable hydrogen production devices.This article analyzes their static and dynamic electrical models integrated with degradation mechanisms.Static models reveal steady-state behavior,while dynamic models capture transient responses to input variations.The developed modeling approach combines the activation and diffusion phenomena,resulting in a novel PEMWE model that closely reflects real-world conditions and enables fast simulations.The electrical model is integrated with the aging model through two key ratios,surface degradation ratio and membrane degradation ratio,which characterize degradation mechanisms affecting electrode and membrane performance.The linear model using second-order Taylor approximation enables the development of a diagnosis approach that can contribute to estimating the remaining useful life of PEMWEs.By associating aging models with electrical models through the proposed ratios,a deeper understanding is achieved regarding how degra-dation phenomena evolve and influence electrolyzer efficiency and durability.The integrated framework enables predictive maintenance strategies,making it valuable for industrial hydrogen production applications.展开更多
In order to search for a suitable anode material used in zinc electrowinning in place of Pb-Ag alloy,Al/Pb-PANI（polyaniline）-WC（tungsten carbide） composite inert anodes were prepared on aluminum alloy substrate by...In order to search for a suitable anode material used in zinc electrowinning in place of Pb-Ag alloy,Al/Pb-PANI（polyaniline）-WC（tungsten carbide） composite inert anodes were prepared on aluminum alloy substrate by double pulse electrodeposition（DPE） of PANI and WC particles with Pb2＋ from an original plating bath.Thereafter,anodic polarization curves,cyclic voltammetry curves and Tafel polarization curves for the composite inert anodes obtained under different PANI concentrations in the original plating bath were measured,and the microstructural features were also investigated by scanning electron microscopy（SEM）.The results show that Al/Pb-PANI-WC composite inert anode obtained under PANI concentration of 20 g/L in the original plating bath possesses uniform microstructures and composition distributions,higher electrocatalytic activity,better reversibility of electrode reaction and corrosion resistance in a synthetic zinc electrowinning electrolyte of 50 g/L Zn2＋,150 g/L H2SO4 at 35 °C.Compared with Pb-1%Ag alloy,the overpotential of oxygen evolutions for the composite inert anode are decreased by 185 mV and 166 mV,respectively,under 500 A/m2 and 1000 A/m2.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
The effects of relative humidity (RH) on a printed circuit board finished with electroless nickel immersion gold (PCB-ENIG) under an adsorbed thin electrolyte layer (ATEL) were investigated in situ via the measurement...The effects of relative humidity (RH) on a printed circuit board finished with electroless nickel immersion gold (PCB-ENIG) under an adsorbed thin electrolyte layer (ATEL) were investigated in situ via the measurement of cathodic polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to clearly elaborate the corrosion behavior of PCB-ENIG in the atmospheric environment. Results indicated that the cathodic process of PCB-ENIG under ATEL was dominated by the reduction of dissolved oxygen, corrosion products, and H2O. The cathodic current density of PCB-ENIG increased progressively with increasing RH. Moreover, its cathodic current density in the solution was greater than that under ATEL. This result demonstrated that the diffusion process was not the controlling step during the limiting reduction of cathodic oxygen. When the polarization potentials were located in a more negative region, the cathodic polarization current density gradually decreased under 75% and 85% RH. Notably, the anodic process became the controlling step in the extremely thin liquid film during the remainder of the experiment.展开更多
Mg-Gd-Y-Zr alloys were purified by filtering purification with and without vacuum. The type, morphology, size distribution and volume fraction of inclusion were analyzed with OM and SEM. The effect of inclusion in Mg-...Mg-Gd-Y-Zr alloys were purified by filtering purification with and without vacuum. The type, morphology, size distribution and volume fraction of inclusion were analyzed with OM and SEM. The effect of inclusion in Mg-Gd-Y-Zr alloys on anticorrosion ability was investigated with salt spray test and electrochemical test. The results show that the inclusions in the alloy can be removed effectively by filtering purification. The average size of inclusions in the alloys is decreased from 12.7 μm to 2.0 μm and the volume fraction of inclusions is reduced from 0.30% to 0.04%. With the decrease of the size of inclusions in the alloys, the corrosion rate of the alloys decreases dramatically from 38.8 g/（m 2 ·d） to 2.4 g/（m 2 ·d） in the salt spray test. The corrosion potential increases while the corrosion current decreases and the polarization resistance increases in the electrochemical tests, which indicates that the anticorrosion ability is improved.展开更多
The electrochemical behaviors of Ta in tetrabutylammonium hydrogen sulfate（TBAHS） ethanol solutions were studied using potentiodynamic polarization,cyclic voltammetry,potentiostatic current time transient and impeda...The electrochemical behaviors of Ta in tetrabutylammonium hydrogen sulfate（TBAHS） ethanol solutions were studied using potentiodynamic polarization,cyclic voltammetry,potentiostatic current time transient and impedance techniques.The results revealed that no active-passive transition is presented in the cyclic voltammogram,and the anodic current density increases with the increase of solution temperature,TBAHS concentration,potential scan rate and water content.The apparent activation energy is about 43.389 kJ/mol and the dissolution process is diffusion-controlled.Potentiostatic measurements showed that the current density gradually decays to a steady value when the potential is low;however,when the potential is higher than a certain value,the current density initially declines to a minimum value and then increases gradually.The resistance of passive film decreases with increasing potential,and inductive loops are presented when the potential is higher than 2.0 V.展开更多
The corrosion behaviours of Mg-5Y-7Gd-1Nd-0.5Zr magnesium alloys prepared by as-casting and extrusion were investigated in 5% NaCl aqueous solution by immersion and electrochemical tests. The microstructure indicates ...The corrosion behaviours of Mg-5Y-7Gd-1Nd-0.5Zr magnesium alloys prepared by as-casting and extrusion were investigated in 5% NaCl aqueous solution by immersion and electrochemical tests. The microstructure indicates the mean grain size of 15 μm for the extruded and 100 μm for the as-cast Mg-5Y-7Gd-1Nd-0.5Zr magnesium alloys. The corrosion morphology of as-cast sample shows pitting corrosion and little filiform corrosion, but that of the extruded sample shows pitting corrosion at the initial stage. The corrosion rate of extruded sample is higher than that of as-cast Mg-5Y-7Gd-1Nd-0.5Zr alloy according to the immersion test. The second phases containing RE acting as cathodes improve the corrosion properties. The corrosion potentials of as-cast and extruded Mg-5Y-7Gd-1Nd-0.5Zr alloys are -1.658 V and -1.591 V, respectively. The origins of the distinctive corrosion behavior of as-cast and extruded Mg-5Y-7Gd-1Nd-0.5Zr Mg alloys were discussed.展开更多
The types, morphologies and distributions of nonmetallic inclusions in Cu-P weathering steels with and without rare earth were analyzed through a quantitative image analyzer, scanning electron microscopy (SEM) and ene...The types, morphologies and distributions of nonmetallic inclusions in Cu-P weathering steels with and without rare earth were analyzed through a quantitative image analyzer, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) attached to SEM. Solid-soluble content of rare earth in the steels was analyzed by non-aqua electroanalysis and ICP. The results showed that rare earth modified the types and the morphologies of inclusions in the weathering steels. The small spherical rare earth oxysulfides and rare earth sulphides replaced the elongated MnS inclusions in the RE weathering steels. The rare earth inclusions dispersedly distributed and most inclusions were smaller than 2 μm in size. The optimum content of RE was 0.0065%-0.016% for 10PCuRE weathering steels containing about 0.002% oxygen and 0.004% sulfur. Solid-soluble content of rare earth in steels was (14-20)×10-6, which can act as a micro-alloying element. The corrosion resistance of 10PCuRE weathering steels and Q235 were studied by dry-wet cyclic immersion test. Their corrosion rates were obtained respectively. The polarization curves and pitting corrosion behaviors of weathering steels with and without rare earth were measured by electrochemical methods. The corrosion resistance of Cu-P weathering steels was improved by adding an appropriate amount of rare earth. Less and fewer rare earth inclusions largely decreased pitting susceptibility and rate of pit propagation. The pitting potential and the resistance against pitting corrosion of the RE weathering steel were significantly improved due to the modification of rare earth to inclusions.展开更多
Effects of La addition on corrosion resistance of hot-dipped galvalume coating steel wire were investigated.The corrosion resistance of Zn-Al-Si-La alloy coatings containing 0, 0.02wt.%, 0.05wt.%, 0.1wt.% and 0.2wt.% ...Effects of La addition on corrosion resistance of hot-dipped galvalume coating steel wire were investigated.The corrosion resistance of Zn-Al-Si-La alloy coatings containing 0, 0.02wt.%, 0.05wt.%, 0.1wt.% and 0.2wt.% La were evaluated by various tests such as copper-accelerated acetic acid salt spray testing（CASS）, immersion test in 3.5% NaCl solution, electrochemical tests including weak polarization curves and electrochemical impedance spectroscopy（EIS） tests, scanning electron microscope（SEM） test and X-ray diffraction（XRD） test.It was found that the corrosion resistance of galvalume coating could be improved by adding proper amounts of La.Meanwhile, the mechanism of the improvement of corrosion resistance by La addition was discussed.展开更多
The effect of Cl^- on the 316L stainless steel in simulated cooling water has been studied using polarization curves, electrochemical impedance spectroscopy （EIS）, Mott- Schottky plot and scanning electron microsco...The effect of Cl^- on the 316L stainless steel in simulated cooling water has been studied using polarization curves, electrochemical impedance spectroscopy （EIS）, Mott- Schottky plot and scanning electron microscopy （SEM） techniques. Cl^- concentrations vary from 200 to 900 mg/L. Results reveal that the corrosion resistance increases with the decrease of Cl^- concentration in simulated cooling water. The increase of Cl^- concentration leads to the shift of the corrosion potential towards the positive direction. Mott-Schottky curves show that in the passive film, Cr2Oa and FeO at the inner layer exhibit P-type but Fe2O3 and CrOa （CrO4^2-） N-type semiconductive properties. The SEM/EDX data demonstrate that elements such as Fe, O, C, Si and Cl as well as the presence of calcium and aluminum are presented on the surface of the metal.展开更多
The effect of HCO3^- concentration on CO2 corrosion was investigated by polarization measurement of potentiodynamic scans and weight-loss method, Under the conditions of high pressure and high temperature, the corrosi...The effect of HCO3^- concentration on CO2 corrosion was investigated by polarization measurement of potentiodynamic scans and weight-loss method, Under the conditions of high pressure and high temperature, the corrosion rate of steel X65 decreased with the increase of HCO3^- concentration, while pH of solution increased. SEM, EDS, and XRD results of the corrosion scales indir cated that the typical FeCO3 crystallite was found at low HCO3^- concentration but Ca（Fe,Mg）（CO3）2 was found at high HCO3^- con- centration. Ca^2＋ and Mg^2＋ are precipitated preferential to Fe^2＋ at high pH value. Potentiodynamic polarization curves showed that the cathodic current density decreases with the increase of HCO3^- concentration at low HCO3^- concentration. When the HCO3^- concentration reaches 0.126 mol/L, increasing HCO3^- concentration promotes cathodic reactions. Anodic behavior is an active process at low HCO3^- concentration and the anodic current density decreases with the increase of HCO3^- concentration. An evident active-passive behavior is exhibited in anodic process at 0.126 mol/L HCO3^-.展开更多
A cathodic plasma electrolytic nitriding(CPEN)treatment with a urea aqueous solution was performed on 316L stainless steel to rapidly improve its surface properties in this work.Test results show that the PEG2000 macr...A cathodic plasma electrolytic nitriding(CPEN)treatment with a urea aqueous solution was performed on 316L stainless steel to rapidly improve its surface properties in this work.Test results show that the PEG2000 macromolecules increased the nitriding energy via enhancing the ability to bond the produced gas film to the metal/electrolyte interface.The cross-sectional morphologies indicate that a thick nitrided layer was obtained when the urea concentration was 543 g I^-1,corresponding to a Vickers hardness 450 HV(0.1),which was 3.5 times larger than that of the substrate.The nitrided layer mainly contained expanded austenite(γN),oxides and iron nitrides(e.g.,Fe3O4 and FeN(0.076)).In terms of its performance,coefficient of friction(COF)of the nitride layer decreased to nearly two-thirds that of the untreated layer,and the passivation current densities of the nitrided sample in a 3.5%NaCl solution decreased by an order of magnitude compared to that of the substrate.Therefore,the approach presented herein provides an attractive way to modify the effect of CPEN in a urea aqueous solution.展开更多
The corrosion behavior of Mg-8Li-3Zn-Al alloy was investigated in neutral 3.5%NaCl aqueous solution by morphology observation and electrochemical tests.The weight loss method was to measure the corrosion rate.The elec...The corrosion behavior of Mg-8Li-3Zn-Al alloy was investigated in neutral 3.5%NaCl aqueous solution by morphology observation and electrochemical tests.The weight loss method was to measure the corrosion rate.The electrochemical results indicated that the corrosion resistance of Mg-8Li-3Zn-Al alloy in 3.5%NaCl solution is poorer than that in distilled water.The Cl-anion leads to the initiation and development of the corrosion pits.And the corrosion products are mainly Mg(OH)_(2).展开更多
The Ti-5Al-2Sn-4Zr-4Mo-2Cr-1Fe(β-CEZ)alloy is considered as a potential structural material in the aviation industry due to its outstanding strength and corrosion resistance.Electrochemical machining(ECM)is an effici...The Ti-5Al-2Sn-4Zr-4Mo-2Cr-1Fe(β-CEZ)alloy is considered as a potential structural material in the aviation industry due to its outstanding strength and corrosion resistance.Electrochemical machining(ECM)is an efficient and low-cost technology for manufacturing theβ-CEZ alloy.In ECM,the machining parameter selection and tool design are based on the electrochemical dissolution behavior of the materials.In this study,the electrochemical dissolution behaviors of theβ-CEZ and Ti-6Al-4V(TC4)alloys in NaNO3solution are discussed.The open circuit potential(OCP),Tafel polarization,potentiodynamic polarization,electrochemical impedance spectroscopy(EIS),and current efficiency curves of theβ-CEZ and TC4 alloys are analyzed.The results show that,compared to the TC4 alloy,the passivation film structure is denser and the charge transfer resistance in the dissolution process is greater for theβ-CEZ alloy.Moreover,the dissolved surface morphology of the two titanium-based alloys under different current densities are analyzed.Under low current densities,theβ-CEZ alloy surface comprises dissolution pits and dissolved products,while the TC4 alloy surface comprises a porous honeycomb structure.Under high current densities,the surface waviness of both the alloys improves and the TC4 alloy surface is flatter and smoother than theβ-CEZ alloy surface.Finally,the electrochemical dissolution models ofβ-CEZ and TC4 alloys are proposed.展开更多
Mineral oxidation leaching in the anode area is the key step in slurry electrolysis.By adopting the slow linear potential scanning method during slurry electrolysis,this study investigated the steady-state polarizatio...Mineral oxidation leaching in the anode area is the key step in slurry electrolysis.By adopting the slow linear potential scanning method during slurry electrolysis,this study investigated the steady-state polarization curve of a pure stibnite mineral on a graphite anode.In addition,the influence of the mineral particle size,liquid–solid ratio,stirring speed,and temperature on the collision oxidation of the mineral with the anode was studied.Based on the different oxidation reactions,the potential range can be divided into three intervals:the low-potential interval with a potential lower than 0.75 V,an intermediatepotential interval with a potential within 0.75–1.2 V,and a high-potential interval with a potential higher than 1.2 V.The collision oxidation of the mineral with the anode occurred in all three intervals.The oxidation of Sb(III)also appeared in the intermediate-and high-potential intervals,and chlorine evolution occurred in the high-potential interval.Therefore,the low-potential interval was determined to be a suitable potential interval for the slurry electrolysis process.In the low-potential interval,the particle size,liquid–solid ratio,and stirring speed had little effect on the oxidation rate of the minerals.As the temperature increased,the stibnite oxidation rate and exchange current density increased.Overall,the direct collision oxidation rate of stibnite was relatively low and the current densities under all the investigated conditions were lower than 0.4 mA·cm^(-2.This indicates that it is difficult to realize industrial production while relying solely on this process.展开更多
The effect of solid-solution treatment on corrosion and electrochemical mechanisms of Mg-15Y alloy in 3.5 wt.% NaCl solution was investigated by electrochemical testing, immersion testing and SEM observation. The resu...The effect of solid-solution treatment on corrosion and electrochemical mechanisms of Mg-15Y alloy in 3.5 wt.% NaCl solution was investigated by electrochemical testing, immersion testing and SEM observation. The results indicated that the corrosion resistance of Mg-15Y sample gradually deteriorated with immersion time increasing, which was consistent with the observation of corrosion morphologies. The solid-solution treatment decreased the amounts of second phase Mg24Ys. The Ecor~ and corrosion rate of as-cast samples were both lower than those of solid solution-treated samples, and both increased with increment of solid solution-treated time. The corrosion mechanism was proposed for the galvanic, pitting and filiform corrosion which varied with the immersion time and solid-solution treatment.展开更多
The corrosion behavior of carbon steel in the medium of marine microorganisms was investigated by electrochemical impedance spectra, polarization curves, and so on. Experimental results showed that the corrosion poten...The corrosion behavior of carbon steel in the medium of marine microorganisms was investigated by electrochemical impedance spectra, polarization curves, and so on. Experimental results showed that the corrosion potential of carbon steel moved in a negative direction in the unpurified marine microorganism solution, and the polarization style of the cathodic process did not change. The electrochemical impedance spectra showed that the impedance value of the electrode decreased in the medium with bacteria, which indicated that the existence of microorganism could accelerate the corrosion progress of carbon steel.展开更多
Fuel cells are considered to be one of the ideal alternatives to traditional fossil energy conversion devices.Membrane electrodes are the core components in the hydrogen fuel cells.Our work reported the synthesis of t...Fuel cells are considered to be one of the ideal alternatives to traditional fossil energy conversion devices.Membrane electrodes are the core components in the hydrogen fuel cells.Our work reported the synthesis of the Pt/C catalysts with different Pt loading,and by changing the Nafion content,hot pressing temperature and hot pressing pressure,the catalyst coated membrane(CCM)spraying process was optimized.Moreover,the three-dimensional structure model of the single battery membrane electrode was studied quantitatively,and the porous membrane electrode with gradient distribution was fabricated under optimized processing conditions,with excellent electrical performance.展开更多
The effects of some inhibitors such as NaOH, NH4OH, Tannic acid and benzotriazole （BTA） were investigated by weight loss, potentiodynamic polarization curve. The results show that NaOH solution is the best one to in...The effects of some inhibitors such as NaOH, NH4OH, Tannic acid and benzotriazole （BTA） were investigated by weight loss, potentiodynamic polarization curve. The results show that NaOH solution is the best one to inhibit the corrosion of Gd in water. After 8880 h immersions in NaOH solution with pH = 10, the surface of the Gd samnle is still silver white. And there are no pitting and weight loss in this process. The same result is in BTA ＋ NaOH solution with pH = 7. After long time immersion, the Gd metal is bright and not corroded. The right inhibitions selection protects Gd from being corroded and ensures that the magnetic refrigerator can work for a long time.展开更多
文摘The polarization curves of mild steel in de-aerated 0.5 mol NaHCO 3+0.5 mol Na 2CO 3 solution with and without erodent particles of 300 g/L of 100 μm alumina have been measured using a rotating cylinder electrode (RCE) apparatus over the range of rotation speeds from 0 to 4 000 r/min. The results show that the mild steel in the de-aerated slurry exhibits classical active/passive polarization behavior. The speed of cylinder rotation has a great effect in the presence of particles on the active dissolution current density. The erosion-corrosion process is severely erosion-dominated for the mild steel. However, the poor corrosion resistance of the mild steel in such turbulent slurries is also significant, especially at lower than 4 m/s.
文摘Proton Exchange Membrane Water Electrolyzers(PEMWE)are efficient and sustainable hydrogen production devices.This article analyzes their static and dynamic electrical models integrated with degradation mechanisms.Static models reveal steady-state behavior,while dynamic models capture transient responses to input variations.The developed modeling approach combines the activation and diffusion phenomena,resulting in a novel PEMWE model that closely reflects real-world conditions and enables fast simulations.The electrical model is integrated with the aging model through two key ratios,surface degradation ratio and membrane degradation ratio,which characterize degradation mechanisms affecting electrode and membrane performance.The linear model using second-order Taylor approximation enables the development of a diagnosis approach that can contribute to estimating the remaining useful life of PEMWEs.By associating aging models with electrical models through the proposed ratios,a deeper understanding is achieved regarding how degra-dation phenomena evolve and influence electrolyzer efficiency and durability.The integrated framework enables predictive maintenance strategies,making it valuable for industrial hydrogen production applications.
基金Project (51004056) supported by the National Natural Science Foundation of ChinaProject (KKZ6201152009) supported by the Opening Foundation of Key Laboratory of Inorganic Coating Materials, ChinaProjects (2011239, 2011240) supported by Analysis and Measurement Research Fund of Kunming University of Science and Technology,China
文摘In order to search for a suitable anode material used in zinc electrowinning in place of Pb-Ag alloy,Al/Pb-PANI（polyaniline）-WC（tungsten carbide） composite inert anodes were prepared on aluminum alloy substrate by double pulse electrodeposition（DPE） of PANI and WC particles with Pb2＋ from an original plating bath.Thereafter,anodic polarization curves,cyclic voltammetry curves and Tafel polarization curves for the composite inert anodes obtained under different PANI concentrations in the original plating bath were measured,and the microstructural features were also investigated by scanning electron microscopy（SEM）.The results show that Al/Pb-PANI-WC composite inert anode obtained under PANI concentration of 20 g/L in the original plating bath possesses uniform microstructures and composition distributions,higher electrocatalytic activity,better reversibility of electrode reaction and corrosion resistance in a synthetic zinc electrowinning electrolyte of 50 g/L Zn2＋,150 g/L H2SO4 at 35 °C.Compared with Pb-1%Ag alloy,the overpotential of oxygen evolutions for the composite inert anode are decreased by 185 mV and 166 mV,respectively,under 500 A/m2 and 1000 A/m2.
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Project(51271032)supported by the National Natural Science Foundation of ChinaProject(2014CB643300)supported by the National Basic Research Program of ChinaProject supported by the National Environmental Corrosion Platform,China
文摘The effects of relative humidity (RH) on a printed circuit board finished with electroless nickel immersion gold (PCB-ENIG) under an adsorbed thin electrolyte layer (ATEL) were investigated in situ via the measurement of cathodic polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to clearly elaborate the corrosion behavior of PCB-ENIG in the atmospheric environment. Results indicated that the cathodic process of PCB-ENIG under ATEL was dominated by the reduction of dissolved oxygen, corrosion products, and H2O. The cathodic current density of PCB-ENIG increased progressively with increasing RH. Moreover, its cathodic current density in the solution was greater than that under ATEL. This result demonstrated that the diffusion process was not the controlling step during the limiting reduction of cathodic oxygen. When the polarization potentials were located in a more negative region, the cathodic polarization current density gradually decreased under 75% and 85% RH. Notably, the anodic process became the controlling step in the extremely thin liquid film during the remainder of the experiment.
基金Project(2007CB613700)supported by the National Basic Research Program of China
文摘Mg-Gd-Y-Zr alloys were purified by filtering purification with and without vacuum. The type, morphology, size distribution and volume fraction of inclusion were analyzed with OM and SEM. The effect of inclusion in Mg-Gd-Y-Zr alloys on anticorrosion ability was investigated with salt spray test and electrochemical test. The results show that the inclusions in the alloy can be removed effectively by filtering purification. The average size of inclusions in the alloys is decreased from 12.7 μm to 2.0 μm and the volume fraction of inclusions is reduced from 0.30% to 0.04%. With the decrease of the size of inclusions in the alloys, the corrosion rate of the alloys decreases dramatically from 38.8 g/（m 2 ·d） to 2.4 g/（m 2 ·d） in the salt spray test. The corrosion potential increases while the corrosion current decreases and the polarization resistance increases in the electrochemical tests, which indicates that the anticorrosion ability is improved.
基金Project(2007AA03Z425)supported by the Hi-tech Research and Development Program of ChinaProject(50404011)supported by the National Natural Science Foundation of China
文摘The electrochemical behaviors of Ta in tetrabutylammonium hydrogen sulfate（TBAHS） ethanol solutions were studied using potentiodynamic polarization,cyclic voltammetry,potentiostatic current time transient and impedance techniques.The results revealed that no active-passive transition is presented in the cyclic voltammogram,and the anodic current density increases with the increase of solution temperature,TBAHS concentration,potential scan rate and water content.The apparent activation energy is about 43.389 kJ/mol and the dissolution process is diffusion-controlled.Potentiostatic measurements showed that the current density gradually decays to a steady value when the potential is low;however,when the potential is higher than a certain value,the current density initially declines to a minimum value and then increases gradually.The resistance of passive film decreases with increasing potential,and inductive loops are presented when the potential is higher than 2.0 V.
基金Project (2011BAE22B01) supported by the National Key Technology R&D Program of China
文摘The corrosion behaviours of Mg-5Y-7Gd-1Nd-0.5Zr magnesium alloys prepared by as-casting and extrusion were investigated in 5% NaCl aqueous solution by immersion and electrochemical tests. The microstructure indicates the mean grain size of 15 μm for the extruded and 100 μm for the as-cast Mg-5Y-7Gd-1Nd-0.5Zr magnesium alloys. The corrosion morphology of as-cast sample shows pitting corrosion and little filiform corrosion, but that of the extruded sample shows pitting corrosion at the initial stage. The corrosion rate of extruded sample is higher than that of as-cast Mg-5Y-7Gd-1Nd-0.5Zr alloy according to the immersion test. The second phases containing RE acting as cathodes improve the corrosion properties. The corrosion potentials of as-cast and extruded Mg-5Y-7Gd-1Nd-0.5Zr alloys are -1.658 V and -1.591 V, respectively. The origins of the distinctive corrosion behavior of as-cast and extruded Mg-5Y-7Gd-1Nd-0.5Zr Mg alloys were discussed.
基金Project supported by Shandong Natural Science Foundation (ZR2010EQ017)
文摘The types, morphologies and distributions of nonmetallic inclusions in Cu-P weathering steels with and without rare earth were analyzed through a quantitative image analyzer, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) attached to SEM. Solid-soluble content of rare earth in the steels was analyzed by non-aqua electroanalysis and ICP. The results showed that rare earth modified the types and the morphologies of inclusions in the weathering steels. The small spherical rare earth oxysulfides and rare earth sulphides replaced the elongated MnS inclusions in the RE weathering steels. The rare earth inclusions dispersedly distributed and most inclusions were smaller than 2 μm in size. The optimum content of RE was 0.0065%-0.016% for 10PCuRE weathering steels containing about 0.002% oxygen and 0.004% sulfur. Solid-soluble content of rare earth in steels was (14-20)×10-6, which can act as a micro-alloying element. The corrosion resistance of 10PCuRE weathering steels and Q235 were studied by dry-wet cyclic immersion test. Their corrosion rates were obtained respectively. The polarization curves and pitting corrosion behaviors of weathering steels with and without rare earth were measured by electrochemical methods. The corrosion resistance of Cu-P weathering steels was improved by adding an appropriate amount of rare earth. Less and fewer rare earth inclusions largely decreased pitting susceptibility and rate of pit propagation. The pitting potential and the resistance against pitting corrosion of the RE weathering steel were significantly improved due to the modification of rare earth to inclusions.
文摘Effects of La addition on corrosion resistance of hot-dipped galvalume coating steel wire were investigated.The corrosion resistance of Zn-Al-Si-La alloy coatings containing 0, 0.02wt.%, 0.05wt.%, 0.1wt.% and 0.2wt.% La were evaluated by various tests such as copper-accelerated acetic acid salt spray testing（CASS）, immersion test in 3.5% NaCl solution, electrochemical tests including weak polarization curves and electrochemical impedance spectroscopy（EIS） tests, scanning electron microscope（SEM） test and X-ray diffraction（XRD） test.It was found that the corrosion resistance of galvalume coating could be improved by adding proper amounts of La.Meanwhile, the mechanism of the improvement of corrosion resistance by La addition was discussed.
基金supported by the National Natural Science Foundation of China (No.50871020)Science & Technology Program of Beijing(No.D09030303790901)
文摘The effect of Cl^- on the 316L stainless steel in simulated cooling water has been studied using polarization curves, electrochemical impedance spectroscopy （EIS）, Mott- Schottky plot and scanning electron microscopy （SEM） techniques. Cl^- concentrations vary from 200 to 900 mg/L. Results reveal that the corrosion resistance increases with the decrease of Cl^- concentration in simulated cooling water. The increase of Cl^- concentration leads to the shift of the corrosion potential towards the positive direction. Mott-Schottky curves show that in the passive film, Cr2Oa and FeO at the inner layer exhibit P-type but Fe2O3 and CrOa （CrO4^2-） N-type semiconductive properties. The SEM/EDX data demonstrate that elements such as Fe, O, C, Si and Cl as well as the presence of calcium and aluminum are presented on the surface of the metal.
基金financially supported by the National Natural Science Foundation of China Key Program (No.50231020)the National Key Basic Research and Development Plan Program (No. G1999065004)
文摘The effect of HCO3^- concentration on CO2 corrosion was investigated by polarization measurement of potentiodynamic scans and weight-loss method, Under the conditions of high pressure and high temperature, the corrosion rate of steel X65 decreased with the increase of HCO3^- concentration, while pH of solution increased. SEM, EDS, and XRD results of the corrosion scales indir cated that the typical FeCO3 crystallite was found at low HCO3^- concentration but Ca（Fe,Mg）（CO3）2 was found at high HCO3^- con- centration. Ca^2＋ and Mg^2＋ are precipitated preferential to Fe^2＋ at high pH value. Potentiodynamic polarization curves showed that the cathodic current density decreases with the increase of HCO3^- concentration at low HCO3^- concentration. When the HCO3^- concentration reaches 0.126 mol/L, increasing HCO3^- concentration promotes cathodic reactions. Anodic behavior is an active process at low HCO3^- concentration and the anodic current density decreases with the increase of HCO3^- concentration. An evident active-passive behavior is exhibited in anodic process at 0.126 mol/L HCO3^-.
基金supported financially by the National Natural Science Foundation of China (No.51771027)the Fundamental Research Funds for the Central Universities (No.FRF-BD-18-019A)+1 种基金the National Key Research and Development Program of China (No. 2017YFB0702100)the National Environmental Corrosion Platform
文摘A cathodic plasma electrolytic nitriding(CPEN)treatment with a urea aqueous solution was performed on 316L stainless steel to rapidly improve its surface properties in this work.Test results show that the PEG2000 macromolecules increased the nitriding energy via enhancing the ability to bond the produced gas film to the metal/electrolyte interface.The cross-sectional morphologies indicate that a thick nitrided layer was obtained when the urea concentration was 543 g I^-1,corresponding to a Vickers hardness 450 HV(0.1),which was 3.5 times larger than that of the substrate.The nitrided layer mainly contained expanded austenite(γN),oxides and iron nitrides(e.g.,Fe3O4 and FeN(0.076)).In terms of its performance,coefficient of friction(COF)of the nitride layer decreased to nearly two-thirds that of the untreated layer,and the passivation current densities of the nitrided sample in a 3.5%NaCl solution decreased by an order of magnitude compared to that of the substrate.Therefore,the approach presented herein provides an attractive way to modify the effect of CPEN in a urea aqueous solution.
基金This work was supported by the financial support of the National Natural Science Foundation of China(No.41276074)National Research Program of China(No.2014CB643304).
文摘The corrosion behavior of Mg-8Li-3Zn-Al alloy was investigated in neutral 3.5%NaCl aqueous solution by morphology observation and electrochemical tests.The weight loss method was to measure the corrosion rate.The electrochemical results indicated that the corrosion resistance of Mg-8Li-3Zn-Al alloy in 3.5%NaCl solution is poorer than that in distilled water.The Cl-anion leads to the initiation and development of the corrosion pits.And the corrosion products are mainly Mg(OH)_(2).
基金supported by the National Natural Science Foundation of China(No.92160301)the Industrial Technology Development Program,China(No.JCKY2021605 B026)。
文摘The Ti-5Al-2Sn-4Zr-4Mo-2Cr-1Fe(β-CEZ)alloy is considered as a potential structural material in the aviation industry due to its outstanding strength and corrosion resistance.Electrochemical machining(ECM)is an efficient and low-cost technology for manufacturing theβ-CEZ alloy.In ECM,the machining parameter selection and tool design are based on the electrochemical dissolution behavior of the materials.In this study,the electrochemical dissolution behaviors of theβ-CEZ and Ti-6Al-4V(TC4)alloys in NaNO3solution are discussed.The open circuit potential(OCP),Tafel polarization,potentiodynamic polarization,electrochemical impedance spectroscopy(EIS),and current efficiency curves of theβ-CEZ and TC4 alloys are analyzed.The results show that,compared to the TC4 alloy,the passivation film structure is denser and the charge transfer resistance in the dissolution process is greater for theβ-CEZ alloy.Moreover,the dissolved surface morphology of the two titanium-based alloys under different current densities are analyzed.Under low current densities,theβ-CEZ alloy surface comprises dissolution pits and dissolved products,while the TC4 alloy surface comprises a porous honeycomb structure.Under high current densities,the surface waviness of both the alloys improves and the TC4 alloy surface is flatter and smoother than theβ-CEZ alloy surface.Finally,the electrochemical dissolution models ofβ-CEZ and TC4 alloys are proposed.
基金supported by the National Key Research&Development Program of China(2019YFC1908404)the Major Science and Technology Projects of Qinghai Province(2018-GXA7)the National Natural Science Foundation of China(51604030)。
文摘Mineral oxidation leaching in the anode area is the key step in slurry electrolysis.By adopting the slow linear potential scanning method during slurry electrolysis,this study investigated the steady-state polarization curve of a pure stibnite mineral on a graphite anode.In addition,the influence of the mineral particle size,liquid–solid ratio,stirring speed,and temperature on the collision oxidation of the mineral with the anode was studied.Based on the different oxidation reactions,the potential range can be divided into three intervals:the low-potential interval with a potential lower than 0.75 V,an intermediatepotential interval with a potential within 0.75–1.2 V,and a high-potential interval with a potential higher than 1.2 V.The collision oxidation of the mineral with the anode occurred in all three intervals.The oxidation of Sb(III)also appeared in the intermediate-and high-potential intervals,and chlorine evolution occurred in the high-potential interval.Therefore,the low-potential interval was determined to be a suitable potential interval for the slurry electrolysis process.In the low-potential interval,the particle size,liquid–solid ratio,and stirring speed had little effect on the oxidation rate of the minerals.As the temperature increased,the stibnite oxidation rate and exchange current density increased.Overall,the direct collision oxidation rate of stibnite was relatively low and the current densities under all the investigated conditions were lower than 0.4 mA·cm^(-2.This indicates that it is difficult to realize industrial production while relying solely on this process.
基金supported by the National Key Technology R&D Program of China (2011BAE22B01)
文摘The effect of solid-solution treatment on corrosion and electrochemical mechanisms of Mg-15Y alloy in 3.5 wt.% NaCl solution was investigated by electrochemical testing, immersion testing and SEM observation. The results indicated that the corrosion resistance of Mg-15Y sample gradually deteriorated with immersion time increasing, which was consistent with the observation of corrosion morphologies. The solid-solution treatment decreased the amounts of second phase Mg24Ys. The Ecor~ and corrosion rate of as-cast samples were both lower than those of solid solution-treated samples, and both increased with increment of solid solution-treated time. The corrosion mechanism was proposed for the galvanic, pitting and filiform corrosion which varied with the immersion time and solid-solution treatment.
基金supported by the Shandong Provincial Doctoral Foundation of China(No.2006BS04021)National Natural Science Foundation of China(No.50672090)Technological Generalship Project of Qingdao(No.05-2-JC-76)
文摘The corrosion behavior of carbon steel in the medium of marine microorganisms was investigated by electrochemical impedance spectra, polarization curves, and so on. Experimental results showed that the corrosion potential of carbon steel moved in a negative direction in the unpurified marine microorganism solution, and the polarization style of the cathodic process did not change. The electrochemical impedance spectra showed that the impedance value of the electrode decreased in the medium with bacteria, which indicated that the existence of microorganism could accelerate the corrosion progress of carbon steel.
基金This work was financially supported by China Petrochemical Corporation(ST 20006-1,ST 20006-2).
文摘Fuel cells are considered to be one of the ideal alternatives to traditional fossil energy conversion devices.Membrane electrodes are the core components in the hydrogen fuel cells.Our work reported the synthesis of the Pt/C catalysts with different Pt loading,and by changing the Nafion content,hot pressing temperature and hot pressing pressure,the catalyst coated membrane(CCM)spraying process was optimized.Moreover,the three-dimensional structure model of the single battery membrane electrode was studied quantitatively,and the porous membrane electrode with gradient distribution was fabricated under optimized processing conditions,with excellent electrical performance.
文摘The effects of some inhibitors such as NaOH, NH4OH, Tannic acid and benzotriazole （BTA） were investigated by weight loss, potentiodynamic polarization curve. The results show that NaOH solution is the best one to inhibit the corrosion of Gd in water. After 8880 h immersions in NaOH solution with pH = 10, the surface of the Gd samnle is still silver white. And there are no pitting and weight loss in this process. The same result is in BTA ＋ NaOH solution with pH = 7. After long time immersion, the Gd metal is bright and not corroded. The right inhibitions selection protects Gd from being corroded and ensures that the magnetic refrigerator can work for a long time.
