This paper reports the comparative evaluation of the corrosion behaviour of AZ31B magnesium alloy under immersion and potentiodynamic polarization test in NaCl solution at different chloride ion concentrations,pH valu...This paper reports the comparative evaluation of the corrosion behaviour of AZ31B magnesium alloy under immersion and potentiodynamic polarization test in NaCl solution at different chloride ion concentrations,pH value and exposure time.The specimens were exposed to immersion and polarization environments in order to evaluate their corrosion rates.Empirical relationship was established to predict the corrosion rate of AZ31B magnesium alloy.Three factors,five level,central composite rotatable design matrix was used to minimize the number of experimental conditions.Response surface methodology was used to develop the relationship.The developed relationship can be effectively used to predict the corrosion rate of AZ31B magnesium alloy at 95%confidence level for both the testing.This research work proves a better corrosion resistance of AZ31B magnesium alloy at the alkaline solution than the acidic and the neutral solutions,moreover,low corrosion rate was found at low concentrated solution and higher exposure time respectively.展开更多
The pitting corrosion behavior of AZ91 alloy before and after micro-oxidation treatment in 3.5%Na Cl solution was investigated by cyclic potentiodynamic polarization(CPDP)and optical and SEM observations of corroded s...The pitting corrosion behavior of AZ91 alloy before and after micro-oxidation treatment in 3.5%Na Cl solution was investigated by cyclic potentiodynamic polarization(CPDP)and optical and SEM observations of corroded surfaces at different polarization potentials.The CPDP results show that both the alloy and the MAO-coated alloy suffer from pitting corrosion and it is difficult for pits to stop growth once the pits initiates.It is revealed that the air-formed Mg O film on AZ91 alloy,the MAO coating along with corrosion products(mainly Mg(OH))formed during CPDP can significantly influence the kinetics of the redox reactions of Mg,and further influence the propagation behavior of pitting corrosion.The optical and SEM images show that the corrosion products on AZ91 alloy are dense and protective but on the MAO-coated corrosion products are very loose.Such observations support the analyses of CPDP results that pits on AZ91 alloy spread to the width whereas pits on MAO-coated alloy propagate to the depth.Overall,pitting corrosion on the MAO-coated alloy can be very severe once the coating ruptures and post-treatments are necessary to provide a promising corrosion protection for the Mg alloys.展开更多
This paper clarifies two issues related to the prior cathodic polarisation treatment(PCPT) for the potentiodynamic polarisation test: whether PCPT can(1) remove the air-formed surface film and(2) affect the polarisati...This paper clarifies two issues related to the prior cathodic polarisation treatment(PCPT) for the potentiodynamic polarisation test: whether PCPT can(1) remove the air-formed surface film and(2) affect the polarisation test results. X-ray photoelectron spectroscopy analyses of fluoride ion-labelled samples show that PCPT cannot remove the surface film completely due to the low reaction rate. Potentiodynamic polarisation tests demonstrate that PCPT with proper operating parameters,-1.0 V SCE for 5 min with subsequent open circuit potential(OCP) stabilisation in this study, is necessary because it can improve the test reproducibility without affecting the corrosion parameters by unifying the initial surface state. However, PCPT with lower potentials, longer time or no OCP stabilisation has significant effects on the electrochemical corrosion parameters due to the hydrogen absorption under the conditions of this study.展开更多
The main purpose of this article is to study the behavior of a metallic electrode in the electrolyte which contains a surface-active substance with the property of adsorbtion-desorbtion, in the galvanodynamic and pote...The main purpose of this article is to study the behavior of a metallic electrode in the electrolyte which contains a surface-active substance with the property of adsorbtion-desorbtion, in the galvanodynamic and potentiodynamic rejimes. The study of the electrochemical behavior of a metallic electrode is carried out by operational impedance method, based on the Ohms low on the interaction between the Laplace-transformed expression of current, voltage and complex resistance (impedance). It is obtained the analytical expression of interface voltage-time dependence in a solution which contains a surface-active indifferent substance with the property of adsorbtion-desorbtion;also it is obtained the analytical expression of current density-time dependence which is passing through electrochemical cell in potentiodynamic regime of functioning of the Frumkin- Melik-Gaykazan model. It is established that the relation between the interface metallic electrode-indifferent electrolyte with property of adsorbtion-desorbtion voltage in the galvanodynamic rejime has the character of second order parabola;the relation between current density which is passing through a cell and time in potentiodynamic rejime of functioning in the Frumkin-Melik-Gaykazan model has exponential character.展开更多
Double-layered microcapsule corrosion inhibitors were developed by sodium monofluorophosphate as the core material,polymethyl methacrylate as the inner wall material,and polyvinyl alcohol as the outer wall material co...Double-layered microcapsule corrosion inhibitors were developed by sodium monofluorophosphate as the core material,polymethyl methacrylate as the inner wall material,and polyvinyl alcohol as the outer wall material combining the solvent evaporation method and spray drying method.The protection by the outer capsule wall was used to prolong the service life of the corrosion inhibitor.The dispersion,encapsulation,thermal stability of microcapsules,and the degradation rate of capsule wall in concrete pore solution were analyzed by ultra-deep field microscopy,scanning electron microscopy,thermal analyzer,and sodium ion release rate analysis.The microcapsules were incorporated into mortar samples containing steel reinforcement,and the effects of double-layered microcapsule corrosion inhibitors on the performance of the cement matrix and the actual corrosion-inhibiting effect were analyzed.The experimental results show that the double-layered microcapsules have a moderate particle size and uniform distribution,and the capsules were completely wrapped.The microcapsules as a whole have good thermal stability below 230 ℃.The monolayer membrane structure microcapsules completely broke within 1 day in the simulated concrete pore solution,and the double-layer membrane structure prolonged the service life of the microcapsules to 80 days in the simulated concrete pore solution before the core material was completely released.The mortar samples containing steel reinforcement incorporated with the double-layered microcapsule corrosion inhibitors still maintained a higher corrosion potential than the monolayer microcapsule corrosion inhibitors control group at 60 days.The incorporation of double-layered microcapsules into the cement matrix has no significant adverse effect on the setting time and early strength.展开更多
The corrosion behaviors of Sn-0.75Cu solder and Sn-0.75Cu/Cu joint in 3.5% NaCl（mass fraction） solution were studied by potentiodynamic polarization test and leaching measurement.The polarization curves indicated th...The corrosion behaviors of Sn-0.75Cu solder and Sn-0.75Cu/Cu joint in 3.5% NaCl（mass fraction） solution were studied by potentiodynamic polarization test and leaching measurement.The polarization curves indicated that the corrosion rate of Sn-0.75Cu solder was lower than that of Sn-0.75Cu/Cu joint.The morphology observation and phase composition analysis on the corroded product at each interesting potential suggested that Sn3O（OH）2Cl2 formed on the surface of Sn-0.75Cu solder at active dissolution stage.As the potential increased from active/passive transition stage,all the surface of Sn-0.75Cu solder was covered by the Sn3O（OH）2Cl2 and some pits appeared after the polarization test.Compared to the Sn-0.75Cu solder alloy,much more Sn3O（OH）2Cl2 formed at active dissolution stage and the pits with bigger size were observed after polarization test for the Sn-0.75Cu/Cu solder joints.The leaching test confirmed that the faster electrochemical corrosion rate resulted in the larger amount of Sn released from the Sn-0.75Cu/Cu solder joints.展开更多
Cored wires and high velocity arc spraying (HVAS) technique were applied to produce high Al content Zn-Al alloy coatings on low carbon steel substrates. The electrochemical corrosion behaviors of Zn, Al and Zn-Al coat...Cored wires and high velocity arc spraying (HVAS) technique were applied to produce high Al content Zn-Al alloy coatings on low carbon steel substrates. The electrochemical corrosion behaviors of Zn, Al and Zn-Al coatings were studied with potentiodynamic measurement in 5 % NaCl solution. Compared with pure Zn, pure Al and Zn-15Al coatings, Zn-26Al coatings show a higher corrosion resistance in salt solution. The potentiodynamic polarization tests show that the corrosion resistance of Zn-Al coatings increases as Al content is raised. Pure Al coating exhibits different electrochemical behaviors with other coatings. The corrosion initiated at the micro-pores of the coating and the underlying corrosion mechanism is very similar to that of the pitting corrosion.展开更多
Potentiodynamic polarization measurement was used to investigate the effects of temperature, dissolved ox- ygen concentration and pH on the electrochemical behavior of X70 pipeline steel in simulated solution accordin...Potentiodynamic polarization measurement was used to investigate the effects of temperature, dissolved ox- ygen concentration and pH on the electrochemical behavior of X70 pipeline steel in simulated solution according to the orthogonal testing method. The results showed that temperature, dissolved oxygen concentration and pH had great influence on corrosion current density （icorr） of X70 steel. Corrosion current density of X70 steel was most influenced by dissolved oxygen concentration in simulated solution. The corrosion degree of X70 steel was the least under the environment of low temperature, deficient oxygen and weak acid.展开更多
The passivation process of X80 pipeline steel in bicarbonate solutions was investigated using potentiodynamic, dynamic electro-chemical impedance spectroscopy （DEIS）, and Mott-Schottky measurements. The results show...The passivation process of X80 pipeline steel in bicarbonate solutions was investigated using potentiodynamic, dynamic electro-chemical impedance spectroscopy （DEIS）, and Mott-Schottky measurements. The results show that the shape of polarization curves changes with concentration. The critical ＇passive＇ concentration is 0.009 mol/L for X80 pipeline steel in bicarbonate solutions. No anodic current peak exists in solutions when the concentration is lower than 0.009 mol/L, whereas there are one and two anodic current peaks when the concentration ranges from 0.009 to 0.05 mol/L and is higher than 0.1 mol/L, respectively. DEIS measurements show that there exist active dissolution range, transition range, pre-passive range, passive layer formation range, passive range, and trans-passive range for X80 pipeline steel in the 0.1 mol/L solutions. The results of DEIS measurements are in complete agreement with the potentiodynamic diagram. An equivalent circuit containing three sub-layers is used to explain the Nyquist plots in the passive range. Analyses are well made for explaining the corresponding fitted capacitance and impedance. The Mott-Schottky plots show that the passive film of X80 pipeline steel is an n-type semiconductor, and capacitance measurements are in good accordance with the results of DEIS experiment.展开更多
In this work, a comparison study on corrosion behavior of extruded near eutectic Al-12.3%Si-0.26%Mg and 6063 alloys has been carried out by mass loss test in 4% H2SO4 aqueous solution in the open air and potentiodynam...In this work, a comparison study on corrosion behavior of extruded near eutectic Al-12.3%Si-0.26%Mg and 6063 alloys has been carried out by mass loss test in 4% H2SO4 aqueous solution in the open air and potentiodynamic polarization test in 3.5 wt.% NaCI aqueous solution. Results indicate that the corrosion resistance of the near eutectic AI-Si-Mg alloy is less than that of 6063 alloy. Macro/microscopy and scanning electron microscopy results clearly show the difference of the corrosion progress of these two alloys in 4% H2SO4 aqueous solution. The corrosion type of 6063 alloy is pitting corrosion. The Mg2Si and AIFeSi particles and surface defects act as nucleation sites for pitting, and the amount and distribution of them have a significant effect on the pitting behavior. For the near eutectic alloy, there are two types of corrosion cells. One is between the extruded primary α-AI and the eutectic, the other is between the eutectic AI and eutectic Si particles. Combination of these two types of corrosion cells leads to a lower corrosion resistance, a higher mass loss of the near eutectic alloy compared with 6063 alloy, and the formation of the paralleling corroded grooves.展开更多
The inhibiting effect of ciprofloxacin,norfloxacin and ofloxacin on the corrosion of mild steel in 1 mol·L-1 HCl and the mechanism were studied at different temperatures using mass loss measurement,electrochemica...The inhibiting effect of ciprofloxacin,norfloxacin and ofloxacin on the corrosion of mild steel in 1 mol·L-1 HCl and the mechanism were studied at different temperatures using mass loss measurement,electrochemical method,and X-ray photoelectron spectroscopy(XPS) .Effective inhibition was shown by mass loss,potentiodynamic polarization and impedance spectroscopy measurement.The corrosion rate of the metal in the mass loss measurement,and the corrosion reaction on cathode and anode in the electrochemical measurement were accelerated when temperature was increased.XPS results showed that the inhibitors adsorbed effectively on the metal surface.展开更多
The hot deformation characteristics and the corrosion behavior of a high-strength low-alloy(HSLA) steel were investigated at deformation temperatures ranging from 800 to 1100 ℃ and strain rates ranging from 0.1 to 10...The hot deformation characteristics and the corrosion behavior of a high-strength low-alloy(HSLA) steel were investigated at deformation temperatures ranging from 800 to 1100 ℃ and strain rates ranging from 0.1 to 10 s-1 using an MMS-200 thermal simulation testing machine. Based on the flow curves from the experiment, the effects of temperature and strain rate on the dynamic recrystallization behavior were analyzed. The flow stress decreased with increasing deformation temperature and decreasing strain rate. With the assistance of the process parameters, constitutive equations were used to obtain the activation energy and hot working equation. The hot deformation activation energy of HSLA steel in this work was 351.87 kJ/mol. The work hardening rate was used to determine the critical stress(strain) or the peak stress(strain). The dependence of these characteristic values on the Zener-Hollomon parameter was found. A dynamic recrystallization kinetics model of the tested HSLA steel was constructed, and the validity of the model was confirmed by the experimental results. Observation of the microstructures indicated that the grain size increased with increasing deformation temperature,which led to a lowered corrosion resistance of the specimens.展开更多
Micro arc oxidation(MAO)coatings were formed on magnesium alloy AZ31B to improve the corrosion resistance using environmental friendly electrolyte solution under single-polar pulse power supply.The effect of electrica...Micro arc oxidation(MAO)coatings were formed on magnesium alloy AZ31B to improve the corrosion resistance using environmental friendly electrolyte solution under single-polar pulse power supply.The effect of electrical parameters of pulse frequency on the coating performance was studied at frequencies of 2.5 Hz,25 Hz and 250 Hz.The coating performance at different frequencies was characterized by scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS)and potentiodynamic polarization testing method.It was found that the corrosion resistance of the MAO coatings was improved when increasing the pulse frequencies from 2.5 Hz to 250 Hz.The corrosion current in 250 Hz case decreased by three orders of magnitude as compared with bare Mg alloy and the corrosion impedance also increased remarkably,means significantly enhanced corrosion resistance than bare Mg alloy.The results give us more insight in the optimization of electrical parameters to improve the MAO coating performance.The MAO technology is attractive for application on magnesium and other light alloys for surface protection in automotive and space industries.展开更多
Corrosion behaviour of the studied Ti12Mo and Ti60Ta alloys with the same Mo equivalent values （12%, mass fraction） together with the currently used metallic biomaterials Cp-Ti were investigated for dental applicati...Corrosion behaviour of the studied Ti12Mo and Ti60Ta alloys with the same Mo equivalent values （12%, mass fraction） together with the currently used metallic biomaterials Cp-Ti were investigated for dental applications. The electrochemical properties of the samples were examined using electrochemical techniques： such as open-circuit potential, potentiodynamic polarization curves and electrochemical impedance spectroscopy （EIS）, in two electrochemical media of artificial saliva and fluoridated artificial saliva （0.1%fluoride ions, F-） at 37 °C. Fluoride is commonly included in toothpastes, odontological gels and dental rinses to prevent dental caries and relieve dental sensitivity. The passive behaviour for all the titanium samples is observed for both solutions. The Ti60Ta alloy appears to possess superior corrosion resistance than the Ti12Mo and Cp-Ti in both electrochemical media.展开更多
The corrosion behavior of the Cu-Ti alloys with different Ti contents in 3.5%(mass fraction)NaCl solution was investigated using electrochemical measurements,immersion tests,mass loss measurements and SEM observation....The corrosion behavior of the Cu-Ti alloys with different Ti contents in 3.5%(mass fraction)NaCl solution was investigated using electrochemical measurements,immersion tests,mass loss measurements and SEM observation.The results show that Ti dissolved in the Cu matrix changes the corrosion process of the alloys.Pure Cu sample exhibits a typical active–passive-transpassive corrosion behavior.The anodic polarization current densities of the Cu-Ti alloys steadily increase with increasing applied potential,indicating that active dissolution of copper proceeds due to the potential difference in the galvanic coupling of Cu and Ti.The increase of Ti content decreases the corrosion resistance of the Cu-Ti alloys.展开更多
In this study,the microstructures,mechanical properties,corrosion behaviors,and biocompatibility of extruded magnesium-zirconiumstrontium-holmium(Mg-Zr-Sr-Ho)alloys were comprehensively investigated.The effect of diff...In this study,the microstructures,mechanical properties,corrosion behaviors,and biocompatibility of extruded magnesium-zirconiumstrontium-holmium(Mg-Zr-Sr-Ho)alloys were comprehensively investigated.The effect of different concentrations of Ho on the microstructural characteristics,tensile and compressive properties,corrosion resistance,and biocompatibility were investigated.The microstructures of the extruded Mg-1Zr-0.5Sr-xHo(x=0.5,1.5,and 4 wt.%)alloys consisted ofα-Mg matrix,fineα-Zr particles,and intermetallic phase particles of Mg_(17)Sr_(2) and Ho_(2)Mg mainly distributed at the grain boundaries.Extensive{1012}tensile twins were observed in the partially recrystallized samples of Mg-1Zr-0.5Sr-0.5Ho and Mg-1Zr-0.5Sr-1.5Ho.Further addition of Ho to 4 wt.%resulted in a complete recrystallization due to activation of the particle stimulated nucleation around the Mg_(17)Sr_(2) particles.The evolution of a rare earth(RE)texture was observed with the Ho addition,which resulted in the weakened basal and prismatic textures.Furthermore,a drastic increase of 200%in tensile elongation and 89%in compressive strain was observed with Ho addition increased from 0.5 to 4 wt%,respectively.The tension-compression yield asymmetry was significantly decreased from 0.62 for Mg-1Zr-0.5Sr-0.5Ho to 0.98 for Mg-1Zr-0.5Sr-4Ho due to the weakening of textures.Corrosion analysis of the extruded Mg-Zr-Sr-Ho alloys revealed the presence of pitting corrosion.A minimum corrosion rate of 4.98 mm y^(−1) was observed in Mg-1Zr-0.5Sr-0.5Ho alloy.The enhanced corrosion resistance is observed due to the presence of Ho_(2)O_(3) in the surface film which reduced galvanic effect.The formation of a stabilized surface film due to the Ho_(2)O_(3) was confirmed through the electrical impedance spectroscopy and XPS analysis.An in vitro cytotoxicity assessment revealed good biocompatibility and cell adhesion in relation to SaOS2 cells.展开更多
In order to study the anodic behavior and microstmctures of A1/Pb-Ag-Co anode during zinc electrowinning, by means of potentiodynamic investigations, scanning electron microscopy （SEM） and X-ray diffraction （XRD） ...In order to study the anodic behavior and microstmctures of A1/Pb-Ag-Co anode during zinc electrowinning, by means of potentiodynamic investigations, scanning electron microscopy （SEM） and X-ray diffraction （XRD） analyses, the mechanism of the anodic processes playing on the surface of A1/Pb-0.8%Ag and A1/Pb-0.75%Ag-0.03%Co anodes prepared by electro-deposition from methyl sulfonic acid bath for zinc electrowinning from model sulphate electrolytes have been measured. On the basis of the cyclic voltammograms obtained, information about the corrosion rate of the composite in PbO2 region has been concluded. The microstructures were also observed by means of SEM and XRD which showed Pb-0.75%Ag-0.03%Co alloy composite coating has uniform and chaotic orientation tetragonal symmetry crystallites of PbSO4, but Pb-0.8%Ag alloy composite coating has well-organized orientation crystallites of PbSO4 concentrated in the certain zones after 24 h of anodic polarization. It is important that Al/Pb-0.75%Ag-0.03%Co anode oxide film consists of non-conductive dense MnO2 and PbSO4 and a, fl-PbO2 penetrated into which, in fact, are the active centers of the oxygen evolution after 24 h of anodic polarization.展开更多
In this study, two types of reinforcing steels(conventional low-carbon steel and a novel duplex alloy steel with Cr and Mo) were exposed to chloride-contaminated extract solutions(ordinary Portland cement(OPC) extract...In this study, two types of reinforcing steels(conventional low-carbon steel and a novel duplex alloy steel with Cr and Mo) were exposed to chloride-contaminated extract solutions(ordinary Portland cement(OPC) extract and alkali-activated slag(AAS) extract) to investigate their pitting corrosion resistance. The results confirm that the pitting corrosion resistance of the alloy steel is much higher than that of the low-carbon steel in both extract solutions with various Na Cl concentrations. Moreover, for each type of steel, the AAS extract contributes to a higher pitting corrosion resistance compared with the OPC extract in the presence of chloride ions, likely because of the formation of flocculent precipitates on the steel surface.展开更多
A number of studies have been reported on the use of nanocrystalline plasma electrolytic nitrocarburising technology for surface hardening of stainless steels for higher corrosion resistance resulted from this techniq...A number of studies have been reported on the use of nanocrystalline plasma electrolytic nitrocarburising technology for surface hardening of stainless steels for higher corrosion resistance resulted from this technique. However, very few studies have focused on the optimization of the nanocrystalline plasma electrolytic nitrocarburising process parameters. In this study, a design of experiment （DOE） technique, the Taguchi method, has been used to optimize the nanocrystalline plasma electrolytic nitrocarburising not only for surface hardening but also for the corrosion protection of 316L austenitic stainless steel by controlling the coating processes factors. The experimental design consisted of four factors （Urea concentration, electrical conductivity of electrolyte, voltage and duration of process）, each containing three levels. Potentiodynamic polarization measurements were carried out to determine the corrosion resistance of the coated samples. The results were analyzed with related software. An analysis of the mean of signal-to-noise （S/N） ratio indicated that the corrosion resistance of nanocrystalline plasma electrolytic nitrocarburised 316L stainless steel was influenced significantly by the levels in the Taguchi orthogonal array. The optimized coating parameters for corrosion resistance are 1150 g/L for urea concentration, 360 mS/cm for electrical conductivity of electrolyte, 260 V for applied voltage, 6 min for treatment time. The percentage of contribution for each factor was determined by the analysis of variance （ANOVA）. The results showed that the applied voltage is the most significant factor affecting the corrosion resistance of the coatings.展开更多
In this work, the corrosion behaviours of the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy and its crystalline counterpart are studied in acidic, neutral, and alkaline solutions by scanning electron microscopy, electrochemic...In this work, the corrosion behaviours of the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy and its crystalline counterpart are studied in acidic, neutral, and alkaline solutions by scanning electron microscopy, electrochemical impedance spectroscopy, and potentiodynamic and potentiostatic polarization tests. X-ray photoelectron spectroscopy and scanning Kelvin probe are employed to characterize the alloy surface. The results show that the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy presents a better corrosion resistance compared to its crystalline counterpart, which is attributed to the uniform energy distribution of the atoms on the amorphous alloy surface, and this presents as a uniform electric potential map to effectively suppress the occurrence of the corrosion cell reaction.展开更多
文摘This paper reports the comparative evaluation of the corrosion behaviour of AZ31B magnesium alloy under immersion and potentiodynamic polarization test in NaCl solution at different chloride ion concentrations,pH value and exposure time.The specimens were exposed to immersion and polarization environments in order to evaluate their corrosion rates.Empirical relationship was established to predict the corrosion rate of AZ31B magnesium alloy.Three factors,five level,central composite rotatable design matrix was used to minimize the number of experimental conditions.Response surface methodology was used to develop the relationship.The developed relationship can be effectively used to predict the corrosion rate of AZ31B magnesium alloy at 95%confidence level for both the testing.This research work proves a better corrosion resistance of AZ31B magnesium alloy at the alkaline solution than the acidic and the neutral solutions,moreover,low corrosion rate was found at low concentrated solution and higher exposure time respectively.
基金the Fund of National Key Laboratory of Remanufacturing[Grant 614005180101]。
文摘The pitting corrosion behavior of AZ91 alloy before and after micro-oxidation treatment in 3.5%Na Cl solution was investigated by cyclic potentiodynamic polarization(CPDP)and optical and SEM observations of corroded surfaces at different polarization potentials.The CPDP results show that both the alloy and the MAO-coated alloy suffer from pitting corrosion and it is difficult for pits to stop growth once the pits initiates.It is revealed that the air-formed Mg O film on AZ91 alloy,the MAO coating along with corrosion products(mainly Mg(OH))formed during CPDP can significantly influence the kinetics of the redox reactions of Mg,and further influence the propagation behavior of pitting corrosion.The optical and SEM images show that the corrosion products on AZ91 alloy are dense and protective but on the MAO-coated corrosion products are very loose.Such observations support the analyses of CPDP results that pits on AZ91 alloy spread to the width whereas pits on MAO-coated alloy propagate to the depth.Overall,pitting corrosion on the MAO-coated alloy can be very severe once the coating ruptures and post-treatments are necessary to provide a promising corrosion protection for the Mg alloys.
基金the National Science and Technology Major Project of China(No.2016ZX05016-004)the National Natural Science Foundation of China(Nos.51801218 and 51571200)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA13040500)。
文摘This paper clarifies two issues related to the prior cathodic polarisation treatment(PCPT) for the potentiodynamic polarisation test: whether PCPT can(1) remove the air-formed surface film and(2) affect the polarisation test results. X-ray photoelectron spectroscopy analyses of fluoride ion-labelled samples show that PCPT cannot remove the surface film completely due to the low reaction rate. Potentiodynamic polarisation tests demonstrate that PCPT with proper operating parameters,-1.0 V SCE for 5 min with subsequent open circuit potential(OCP) stabilisation in this study, is necessary because it can improve the test reproducibility without affecting the corrosion parameters by unifying the initial surface state. However, PCPT with lower potentials, longer time or no OCP stabilisation has significant effects on the electrochemical corrosion parameters due to the hydrogen absorption under the conditions of this study.
文摘The main purpose of this article is to study the behavior of a metallic electrode in the electrolyte which contains a surface-active substance with the property of adsorbtion-desorbtion, in the galvanodynamic and potentiodynamic rejimes. The study of the electrochemical behavior of a metallic electrode is carried out by operational impedance method, based on the Ohms low on the interaction between the Laplace-transformed expression of current, voltage and complex resistance (impedance). It is obtained the analytical expression of interface voltage-time dependence in a solution which contains a surface-active indifferent substance with the property of adsorbtion-desorbtion;also it is obtained the analytical expression of current density-time dependence which is passing through electrochemical cell in potentiodynamic regime of functioning of the Frumkin- Melik-Gaykazan model. It is established that the relation between the interface metallic electrode-indifferent electrolyte with property of adsorbtion-desorbtion voltage in the galvanodynamic rejime has the character of second order parabola;the relation between current density which is passing through a cell and time in potentiodynamic rejime of functioning in the Frumkin-Melik-Gaykazan model has exponential character.
基金Fund by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (No.2018YFD1101002-03)。
文摘Double-layered microcapsule corrosion inhibitors were developed by sodium monofluorophosphate as the core material,polymethyl methacrylate as the inner wall material,and polyvinyl alcohol as the outer wall material combining the solvent evaporation method and spray drying method.The protection by the outer capsule wall was used to prolong the service life of the corrosion inhibitor.The dispersion,encapsulation,thermal stability of microcapsules,and the degradation rate of capsule wall in concrete pore solution were analyzed by ultra-deep field microscopy,scanning electron microscopy,thermal analyzer,and sodium ion release rate analysis.The microcapsules were incorporated into mortar samples containing steel reinforcement,and the effects of double-layered microcapsule corrosion inhibitors on the performance of the cement matrix and the actual corrosion-inhibiting effect were analyzed.The experimental results show that the double-layered microcapsules have a moderate particle size and uniform distribution,and the capsules were completely wrapped.The microcapsules as a whole have good thermal stability below 230 ℃.The monolayer membrane structure microcapsules completely broke within 1 day in the simulated concrete pore solution,and the double-layer membrane structure prolonged the service life of the microcapsules to 80 days in the simulated concrete pore solution before the core material was completely released.The mortar samples containing steel reinforcement incorporated with the double-layered microcapsule corrosion inhibitors still maintained a higher corrosion potential than the monolayer microcapsule corrosion inhibitors control group at 60 days.The incorporation of double-layered microcapsules into the cement matrix has no significant adverse effect on the setting time and early strength.
基金Project (2005DKA10400-Z23) supported by Chinese National Science and Technology InfrastructureProject (DUT10R:(3)65) supported by Fundamental Research Funds for the Central Universities,China
文摘The corrosion behaviors of Sn-0.75Cu solder and Sn-0.75Cu/Cu joint in 3.5% NaCl（mass fraction） solution were studied by potentiodynamic polarization test and leaching measurement.The polarization curves indicated that the corrosion rate of Sn-0.75Cu solder was lower than that of Sn-0.75Cu/Cu joint.The morphology observation and phase composition analysis on the corroded product at each interesting potential suggested that Sn3O（OH）2Cl2 formed on the surface of Sn-0.75Cu solder at active dissolution stage.As the potential increased from active/passive transition stage,all the surface of Sn-0.75Cu solder was covered by the Sn3O（OH）2Cl2 and some pits appeared after the polarization test.Compared to the Sn-0.75Cu solder alloy,much more Sn3O（OH）2Cl2 formed at active dissolution stage and the pits with bigger size were observed after polarization test for the Sn-0.75Cu/Cu solder joints.The leaching test confirmed that the faster electrochemical corrosion rate resulted in the larger amount of Sn released from the Sn-0.75Cu/Cu solder joints.
基金Project(50235030)supported by the National Natural Science Foundation of China
文摘Cored wires and high velocity arc spraying (HVAS) technique were applied to produce high Al content Zn-Al alloy coatings on low carbon steel substrates. The electrochemical corrosion behaviors of Zn, Al and Zn-Al coatings were studied with potentiodynamic measurement in 5 % NaCl solution. Compared with pure Zn, pure Al and Zn-15Al coatings, Zn-26Al coatings show a higher corrosion resistance in salt solution. The potentiodynamic polarization tests show that the corrosion resistance of Zn-Al coatings increases as Al content is raised. Pure Al coating exhibits different electrochemical behaviors with other coatings. The corrosion initiated at the micro-pores of the coating and the underlying corrosion mechanism is very similar to that of the pitting corrosion.
基金Item Sponsored by National Science and Technology Infrastructure Platforms Construction Projects of China (2005DKA10400)National Science and Technology Support 11th Five-Year Plan of China(2006BAK02B01)
文摘Potentiodynamic polarization measurement was used to investigate the effects of temperature, dissolved ox- ygen concentration and pH on the electrochemical behavior of X70 pipeline steel in simulated solution according to the orthogonal testing method. The results showed that temperature, dissolved oxygen concentration and pH had great influence on corrosion current density （icorr） of X70 steel. Corrosion current density of X70 steel was most influenced by dissolved oxygen concentration in simulated solution. The corrosion degree of X70 steel was the least under the environment of low temperature, deficient oxygen and weak acid.
基金supported by the National Science and Technology Infrastructure Platforms Construction Projects (No.2005DKA10400)
文摘The passivation process of X80 pipeline steel in bicarbonate solutions was investigated using potentiodynamic, dynamic electro-chemical impedance spectroscopy （DEIS）, and Mott-Schottky measurements. The results show that the shape of polarization curves changes with concentration. The critical ＇passive＇ concentration is 0.009 mol/L for X80 pipeline steel in bicarbonate solutions. No anodic current peak exists in solutions when the concentration is lower than 0.009 mol/L, whereas there are one and two anodic current peaks when the concentration ranges from 0.009 to 0.05 mol/L and is higher than 0.1 mol/L, respectively. DEIS measurements show that there exist active dissolution range, transition range, pre-passive range, passive layer formation range, passive range, and trans-passive range for X80 pipeline steel in the 0.1 mol/L solutions. The results of DEIS measurements are in complete agreement with the potentiodynamic diagram. An equivalent circuit containing three sub-layers is used to explain the Nyquist plots in the passive range. Analyses are well made for explaining the corresponding fitted capacitance and impedance. The Mott-Schottky plots show that the passive film of X80 pipeline steel is an n-type semiconductor, and capacitance measurements are in good accordance with the results of DEIS experiment.
基金supported by Jiangsu Graduated-student Innovation Program of China(No.CXZZ-0146)the Scientific Research Foundation of Graduate School of Southeast University
文摘In this work, a comparison study on corrosion behavior of extruded near eutectic Al-12.3%Si-0.26%Mg and 6063 alloys has been carried out by mass loss test in 4% H2SO4 aqueous solution in the open air and potentiodynamic polarization test in 3.5 wt.% NaCI aqueous solution. Results indicate that the corrosion resistance of the near eutectic AI-Si-Mg alloy is less than that of 6063 alloy. Macro/microscopy and scanning electron microscopy results clearly show the difference of the corrosion progress of these two alloys in 4% H2SO4 aqueous solution. The corrosion type of 6063 alloy is pitting corrosion. The Mg2Si and AIFeSi particles and surface defects act as nucleation sites for pitting, and the amount and distribution of them have a significant effect on the pitting behavior. For the near eutectic alloy, there are two types of corrosion cells. One is between the extruded primary α-AI and the eutectic, the other is between the eutectic AI and eutectic Si particles. Combination of these two types of corrosion cells leads to a lower corrosion resistance, a higher mass loss of the near eutectic alloy compared with 6063 alloy, and the formation of the paralleling corroded grooves.
基金Supported by the National Science ＆ Technology Pillar Program（082603101c） China Postdoctoral Science Foundation （O92623101H）+2 种基金 Shandong Postdoctoral Foundation（200902040） Open Project Program of Marine Corrosion and Protection Research Center of Institute of Oceanology Chinese Academy of Science（200901005） Doctor Foundation of University of Jinan（XBS0899）
文摘The inhibiting effect of ciprofloxacin,norfloxacin and ofloxacin on the corrosion of mild steel in 1 mol·L-1 HCl and the mechanism were studied at different temperatures using mass loss measurement,electrochemical method,and X-ray photoelectron spectroscopy(XPS) .Effective inhibition was shown by mass loss,potentiodynamic polarization and impedance spectroscopy measurement.The corrosion rate of the metal in the mass loss measurement,and the corrosion reaction on cathode and anode in the electrochemical measurement were accelerated when temperature was increased.XPS results showed that the inhibitors adsorbed effectively on the metal surface.
基金supported financially by the Fundamental Research Funds for the Central Universities (Nos. HEUCFP201719 and HEUCFP201731)
文摘The hot deformation characteristics and the corrosion behavior of a high-strength low-alloy(HSLA) steel were investigated at deformation temperatures ranging from 800 to 1100 ℃ and strain rates ranging from 0.1 to 10 s-1 using an MMS-200 thermal simulation testing machine. Based on the flow curves from the experiment, the effects of temperature and strain rate on the dynamic recrystallization behavior were analyzed. The flow stress decreased with increasing deformation temperature and decreasing strain rate. With the assistance of the process parameters, constitutive equations were used to obtain the activation energy and hot working equation. The hot deformation activation energy of HSLA steel in this work was 351.87 kJ/mol. The work hardening rate was used to determine the critical stress(strain) or the peak stress(strain). The dependence of these characteristic values on the Zener-Hollomon parameter was found. A dynamic recrystallization kinetics model of the tested HSLA steel was constructed, and the validity of the model was confirmed by the experimental results. Observation of the microstructures indicated that the grain size increased with increasing deformation temperature,which led to a lowered corrosion resistance of the specimens.
基金This work performed by the author was financially sup-ported by Singapore Ministry of Education innovation Fund(MOE2010-IF-027).
文摘Micro arc oxidation(MAO)coatings were formed on magnesium alloy AZ31B to improve the corrosion resistance using environmental friendly electrolyte solution under single-polar pulse power supply.The effect of electrical parameters of pulse frequency on the coating performance was studied at frequencies of 2.5 Hz,25 Hz and 250 Hz.The coating performance at different frequencies was characterized by scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS)and potentiodynamic polarization testing method.It was found that the corrosion resistance of the MAO coatings was improved when increasing the pulse frequencies from 2.5 Hz to 250 Hz.The corrosion current in 250 Hz case decreased by three orders of magnitude as compared with bare Mg alloy and the corrosion impedance also increased remarkably,means significantly enhanced corrosion resistance than bare Mg alloy.The results give us more insight in the optimization of electrical parameters to improve the MAO coating performance.The MAO technology is attractive for application on magnesium and other light alloys for surface protection in automotive and space industries.
基金Project (PN-II-ID-PCE-2011-3-0218) supported by the Romanian National Authority for Scientific Research,CNCS-UEFISCDI
文摘Corrosion behaviour of the studied Ti12Mo and Ti60Ta alloys with the same Mo equivalent values （12%, mass fraction） together with the currently used metallic biomaterials Cp-Ti were investigated for dental applications. The electrochemical properties of the samples were examined using electrochemical techniques： such as open-circuit potential, potentiodynamic polarization curves and electrochemical impedance spectroscopy （EIS）, in two electrochemical media of artificial saliva and fluoridated artificial saliva （0.1%fluoride ions, F-） at 37 °C. Fluoride is commonly included in toothpastes, odontological gels and dental rinses to prevent dental caries and relieve dental sensitivity. The passive behaviour for all the titanium samples is observed for both solutions. The Ti60Ta alloy appears to possess superior corrosion resistance than the Ti12Mo and Cp-Ti in both electrochemical media.
基金Project(51374151)supported by the National Natural Science Foundation of China
文摘The corrosion behavior of the Cu-Ti alloys with different Ti contents in 3.5%(mass fraction)NaCl solution was investigated using electrochemical measurements,immersion tests,mass loss measurements and SEM observation.The results show that Ti dissolved in the Cu matrix changes the corrosion process of the alloys.Pure Cu sample exhibits a typical active–passive-transpassive corrosion behavior.The anodic polarization current densities of the Cu-Ti alloys steadily increase with increasing applied potential,indicating that active dissolution of copper proceeds due to the potential difference in the galvanic coupling of Cu and Ti.The increase of Ti content decreases the corrosion resistance of the Cu-Ti alloys.
基金the financial support for this research by the Australian Research Council(ARC)through the Future Fellowship(FT160100252)the Discovery Project(DP170102557)。
文摘In this study,the microstructures,mechanical properties,corrosion behaviors,and biocompatibility of extruded magnesium-zirconiumstrontium-holmium(Mg-Zr-Sr-Ho)alloys were comprehensively investigated.The effect of different concentrations of Ho on the microstructural characteristics,tensile and compressive properties,corrosion resistance,and biocompatibility were investigated.The microstructures of the extruded Mg-1Zr-0.5Sr-xHo(x=0.5,1.5,and 4 wt.%)alloys consisted ofα-Mg matrix,fineα-Zr particles,and intermetallic phase particles of Mg_(17)Sr_(2) and Ho_(2)Mg mainly distributed at the grain boundaries.Extensive{1012}tensile twins were observed in the partially recrystallized samples of Mg-1Zr-0.5Sr-0.5Ho and Mg-1Zr-0.5Sr-1.5Ho.Further addition of Ho to 4 wt.%resulted in a complete recrystallization due to activation of the particle stimulated nucleation around the Mg_(17)Sr_(2) particles.The evolution of a rare earth(RE)texture was observed with the Ho addition,which resulted in the weakened basal and prismatic textures.Furthermore,a drastic increase of 200%in tensile elongation and 89%in compressive strain was observed with Ho addition increased from 0.5 to 4 wt%,respectively.The tension-compression yield asymmetry was significantly decreased from 0.62 for Mg-1Zr-0.5Sr-0.5Ho to 0.98 for Mg-1Zr-0.5Sr-4Ho due to the weakening of textures.Corrosion analysis of the extruded Mg-Zr-Sr-Ho alloys revealed the presence of pitting corrosion.A minimum corrosion rate of 4.98 mm y^(−1) was observed in Mg-1Zr-0.5Sr-0.5Ho alloy.The enhanced corrosion resistance is observed due to the presence of Ho_(2)O_(3) in the surface film which reduced galvanic effect.The formation of a stabilized surface film due to the Ho_(2)O_(3) was confirmed through the electrical impedance spectroscopy and XPS analysis.An in vitro cytotoxicity assessment revealed good biocompatibility and cell adhesion in relation to SaOS2 cells.
基金Project(51004056)supported by the National Natural Science Foundation of China
文摘In order to study the anodic behavior and microstmctures of A1/Pb-Ag-Co anode during zinc electrowinning, by means of potentiodynamic investigations, scanning electron microscopy （SEM） and X-ray diffraction （XRD） analyses, the mechanism of the anodic processes playing on the surface of A1/Pb-0.8%Ag and A1/Pb-0.75%Ag-0.03%Co anodes prepared by electro-deposition from methyl sulfonic acid bath for zinc electrowinning from model sulphate electrolytes have been measured. On the basis of the cyclic voltammograms obtained, information about the corrosion rate of the composite in PbO2 region has been concluded. The microstructures were also observed by means of SEM and XRD which showed Pb-0.75%Ag-0.03%Co alloy composite coating has uniform and chaotic orientation tetragonal symmetry crystallites of PbSO4, but Pb-0.8%Ag alloy composite coating has well-organized orientation crystallites of PbSO4 concentrated in the certain zones after 24 h of anodic polarization. It is important that Al/Pb-0.75%Ag-0.03%Co anode oxide film consists of non-conductive dense MnO2 and PbSO4 and a, fl-PbO2 penetrated into which, in fact, are the active centers of the oxygen evolution after 24 h of anodic polarization.
基金financially supported by the National Natural Science Foundation of China (Nos.51461135001 and 51678144)the Major State Basic Research Development Program of China (No.2015CB655100)+2 种基金the Natural Science Foundation of Jiangsu Province (No.BK20161420)the Industry-University Research Cooperative Innovation Fund of Jiangsu Province (No.BY2013091)the China-Japan Research Cooperative Program by Ministry of Science and Technology of China (No.2016YFE0118200)
文摘In this study, two types of reinforcing steels(conventional low-carbon steel and a novel duplex alloy steel with Cr and Mo) were exposed to chloride-contaminated extract solutions(ordinary Portland cement(OPC) extract and alkali-activated slag(AAS) extract) to investigate their pitting corrosion resistance. The results confirm that the pitting corrosion resistance of the alloy steel is much higher than that of the low-carbon steel in both extract solutions with various Na Cl concentrations. Moreover, for each type of steel, the AAS extract contributes to a higher pitting corrosion resistance compared with the OPC extract in the presence of chloride ions, likely because of the formation of flocculent precipitates on the steel surface.
文摘A number of studies have been reported on the use of nanocrystalline plasma electrolytic nitrocarburising technology for surface hardening of stainless steels for higher corrosion resistance resulted from this technique. However, very few studies have focused on the optimization of the nanocrystalline plasma electrolytic nitrocarburising process parameters. In this study, a design of experiment （DOE） technique, the Taguchi method, has been used to optimize the nanocrystalline plasma electrolytic nitrocarburising not only for surface hardening but also for the corrosion protection of 316L austenitic stainless steel by controlling the coating processes factors. The experimental design consisted of four factors （Urea concentration, electrical conductivity of electrolyte, voltage and duration of process）, each containing three levels. Potentiodynamic polarization measurements were carried out to determine the corrosion resistance of the coated samples. The results were analyzed with related software. An analysis of the mean of signal-to-noise （S/N） ratio indicated that the corrosion resistance of nanocrystalline plasma electrolytic nitrocarburised 316L stainless steel was influenced significantly by the levels in the Taguchi orthogonal array. The optimized coating parameters for corrosion resistance are 1150 g/L for urea concentration, 360 mS/cm for electrical conductivity of electrolyte, 260 V for applied voltage, 6 min for treatment time. The percentage of contribution for each factor was determined by the analysis of variance （ANOVA）. The results showed that the applied voltage is the most significant factor affecting the corrosion resistance of the coatings.
文摘In this work, the corrosion behaviours of the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy and its crystalline counterpart are studied in acidic, neutral, and alkaline solutions by scanning electron microscopy, electrochemical impedance spectroscopy, and potentiodynamic and potentiostatic polarization tests. X-ray photoelectron spectroscopy and scanning Kelvin probe are employed to characterize the alloy surface. The results show that the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy presents a better corrosion resistance compared to its crystalline counterpart, which is attributed to the uniform energy distribution of the atoms on the amorphous alloy surface, and this presents as a uniform electric potential map to effectively suppress the occurrence of the corrosion cell reaction.
