The effect of microstructure and passive film on the corrosion resistance of 2507 super duplex stainless steel(SDSS)in simulated marine environment was investigated by electrochemical measurements,periodic wet–dry cy...The effect of microstructure and passive film on the corrosion resistance of 2507 super duplex stainless steel(SDSS)in simulated marine environment was investigated by electrochemical measurements,periodic wet–dry cyclic corrosion test,scanning Kelvin probe force microscopy,atomic force microscopy,and X-ray photoelectron spectrometry.The results show that the occupation ratio ofγphase increases with the decrease in cooling rate,whereas the content ofαphase reduces gradually.In addition,theσprecipitated phase only emerges in the annealed steel.The pitting sensitivity and corrosion rate of 2507 SDSS reduce first and then increase as the cooling rate decreases.Theσprecipitated phase drastically reduces the protective ability of the passive film and facilitates micro-galvanic corrosion of the annealed steel.For various microstructures,the pits are preferentially distributed within theσandγphases.The corrosion resistance of 2507 SDSS prepared by different cooling methods is closely related to the microstructure and structure(stability and homogeneity)of the passive film.Normalized steel shows an optimal corrosion resistance,followed by the quenched and annealed steels.展开更多
To study the effect of free radical photocurable passivation film modified by titanate coupling agent for hot-plated aluminum-zinc plate,trimethylpropane triacrylate(TMPTA)and 2-phenoxyethyl acrylate were used as acti...To study the effect of free radical photocurable passivation film modified by titanate coupling agent for hot-plated aluminum-zinc plate,trimethylpropane triacrylate(TMPTA)and 2-phenoxyethyl acrylate were used as active diluents,a mixture of modified epoxy acrylate and modified polyester acrylate in a certain proportion was used as an oligomer,2-methyl-1-[4-(methylothyl)benzene]-2-morpholine acetone(907)was used as a free radical photoinitiator,isopropyl thioxanthone(ITX)was used as sensitizer,and bis(dioctyl phosphate acyl)titanate ethyltitanate acrylamide chelate(FD-812)was used as corrosion inhibitor modifier.After UV-curing,the passivation film was characterized by neutral salt spray test,electrochemical testing and other methods.The general performance of the passivation film may meet the requirements of downstream users of hot aluminum-zinc steel plate.The neutral salt spray test,electrochemical testing and microscopic surface morphology analysis of passivation film are in agreement.The introduction of titanate components may effectively promote the photocuring of free radicals.There have been few reports on the titanate coupling which is added to UV-curing coating formula.The titanate coupling agent contains acrylamide groups and terminal amine groups,acrylamide group has oligomer and crosslinking monomer,the terminal tertiary amine groups can provide hydrogen protons,reduce oxygen polymerization,and a phosphating film is formed on the surface of the metal substrate to improve the adhesion and corrosion resistance of the coating.展开更多
The properties of the films formed in the electrolyte of PC/DME LiClO4 on two kinds of Carbon materials were examined by cathodic polarization measurements. The result suggested that the films on both carbon electrode...The properties of the films formed in the electrolyte of PC/DME LiClO4 on two kinds of Carbon materials were examined by cathodic polarization measurements. The result suggested that the films on both carbon electrodes have different morphology which resulted in the different cell performance of the two carbon anodes.展开更多
Passive films formed on sensitized stainless steel in sulphuric acid solutions have been studied using photoefectrochemical techniques. The results of the photocurrent measurement indicate that the passive films on se...Passive films formed on sensitized stainless steel in sulphuric acid solutions have been studied using photoefectrochemical techniques. The results of the photocurrent measurement indicate that the passive films on sensitized stainless steel are characterised with n-type or p-type semiconductor in different potential regions. The difference in the photoelectrochemical behaviour can be interpreted assuming that the passive film is an iron-chromium oxide solid solution associated with various hydration degrees of the Cr(Ⅲ) oxides at various展开更多
The surface treatment technology of hot aluminum-zinc steel plate and UV curing technology may be effectively combined in the present research. According to different light curing mechanisms, different formulations fr...The surface treatment technology of hot aluminum-zinc steel plate and UV curing technology may be effectively combined in the present research. According to different light curing mechanisms, different formulations from UV curing surface treatment agents can be applied to the surface treatment of hot aluminum-zinc steel plate, mainly including 3-ethyl-3-benzoxy-methyl oxacyclobutane (TCM 104) and 3,4-epoxy-cyclohexylformic acid -3',4'-epoxy-cyclohexyl methyl ester (UVR 6110) as active diluents, high molecular weight polyfunctional oxacyclobutane as oligomer, triaryl sulfonium salt as a cationic photoinitiator, and an anthracene compound as a sensitizer. 385 nm LED lamp used as a radiation resource, the effects of the proportion of active diluent, the type and amount of photoinitiator, the amount of sensitizer, the curing temperature, and the amount of nano-SiO<sub>2</sub> on the photocuring rate were investigated by photoper-scanning differential calorimetry (Photo-DSC). The experimental results show that the system has the fastest photocuring rate under the conditions of 8:2 ratio of TCM 104 to UVR 6110, 2.5% photoinitiator, 0.6% sensitizer, 0.2% nano-SiO<sub>2</sub> additive, and 80˚C curing temperature. Based on addition of the appropriate number of various additives, the cationic photocuring surface treatment solution was prepared and further coated on the hot-dip galvalume steel plates. After curing, the passivation films were characterized by neutral salt spray test (NSST), Fourier transform infrared spectroscopy (FT-IR), electrochemical testing and other methods. The results show that the formulations could be cured at an energy of 150 mJ/cm<sup>2</sup>, and the overall performance of the passivation film could meet with the requirements of the downstream users.展开更多
Air nanobubbles(A-NBs)were used to inhibit the brass corrosion in circulating cooling water for the first time in the study.The results of mass loss method and electrochemical method showed that A-NBs had the obvious ...Air nanobubbles(A-NBs)were used to inhibit the brass corrosion in circulating cooling water for the first time in the study.The results of mass loss method and electrochemical method showed that A-NBs had the obvious corrosion inhibition effect.The inhibition rate reached 52%at 35℃.The impedance and surface characterization results of corrosion samples indicated that the corrosion inhibition mechanisms of A-NBs mainly included adsorption of corrosion ions,promoting the formation of the passivation film on metal surface and the formation of the bubble layer and scale film on metal surface.A-NBs are potential excellent corrosion inhibitors.展开更多
The present study investigates the mechanical and in-vitro corrosion behavior of Mg-4Zn-0.5Ca-0.8Mn alloy in optimum homogenized conditions.The optimization of the homogenization parameters has been carried out employ...The present study investigates the mechanical and in-vitro corrosion behavior of Mg-4Zn-0.5Ca-0.8Mn alloy in optimum homogenized conditions.The optimization of the homogenization parameters has been carried out employing thermodynamic calculations and kinetic modeling.The model utilizes the inter-diffusivity of the solute elements and predicts that∼6–24 h of homogenization at 633 K effectively redistributes the elements in the Mg matrix.Based on the insights obtained from the simulations,the as-cast Mg-4Zn-0.5Ca-0.8Mn alloy was subjected to homogenization heat treatment process for 6–24h.The microstructural study through optical microscopy and scanning electron microscopy(SEM)revealed that the interconnected network of second phase precipitates substantially dissolve within 24 h,implying adequate homogenization.Moreover,fine Mg-Zn based precipitates with varied morphology and phase fractions also evolved during homogenization treatment,as confirmed through SEM and transmission electron microscopy.In the 12 h homogenized specimen,the highest fraction of uniformly dispersed fine precipitates resulted in the highest strength(∼225 MPa).On the other hand,a substantial disruption in coarse precipitate network and lower aspect ratio of fine Mg-Zn precipitates led to the highest ductility(∼8%)in this specimen.In the 24 h homogenized specimen,the ductility reduced marginally owing to higher aspect ratio of fine precipitates.The immersion and electrochemical tests(viz.,potentiodynamic polarization and electrochemical impedance spectroscopy)carried out in Hank’s solution revealed that the 24 h homogenized specimen exhibits the best corrosion properties.The least fraction of Ca_(2)Mg_(6)Zn_(3)phase with maximum disruption in interconnectivity,in combination with a small fraction of fine equilibrium MgZn_(2)precipitates,resulted in suppression of localized corrosion in this specimen.This promotes the formation of the most stable and compact product layer over the specimen,resulting in the highest corrosion resistance.展开更多
The corrosion behaviour of bronze alloy prepared by equal channel angular pressing(ECAP) was investigated in 3.5 wt. % Na Cl solution.Immersion corrosion tests and different electrochemical techniques were carried out...The corrosion behaviour of bronze alloy prepared by equal channel angular pressing(ECAP) was investigated in 3.5 wt. % Na Cl solution.Immersion corrosion tests and different electrochemical techniques were carried out. The results showed that ECAPed bronze samples exhibited higher corrosion resistance compared with the as-cast alloy and the passive current density decreased with increasing number of passes. Moreover,the morphology of alloys indicated that the corrosion damage on the surface of ECAPed bronze was smooth and uniform while the as-cast alloy suffered from selective corrosion.展开更多
As a material with good corrosion resistance,5083 aluminum alloy has a great application prospect in marine environment.In this work,the corrosion characteristics of 5083 aluminum alloy in seawater containing phosphat...As a material with good corrosion resistance,5083 aluminum alloy has a great application prospect in marine environment.In this work,the corrosion characteristics of 5083 aluminum alloy in seawater containing phosphate were investigated with Potentiodynamic Polarization,Electrochemical Impedance Spectroscopy (EIS),Scanning Electron Microscope (SEM),Energy Dispersive Spectroscopy Analysis (EDSA),X-ray Photoelectron Spectroscopy (XPS) and Laser Confocal Microscope.The results indicated that the effects of phosphate in seawater were two-fold.Firstly,phosphate slightly accelerated the corrosion of 5083 in seawater in the early stage of corrosion.HPO_4~(2-)competed with OH~-in the adsorption process on the alloy surface,which weakened the contact between OH~-and Al~(3+)near the interface of the alloy,and inhibited the formation as well as the self-repair of the passive film,thus accelerating the activation dissolution process.Compared with the natural seawater,the charge transfer resistance of 5083 in the seawater containing phosphate decreased faster during the early stage of corrosion,and the corrosion current density i_(corr) was higher in seawater containing phosphate.On the other hand,the addition of phosphate would not affect the cluster distribution of the second phase of 5083 in seawater,but it changed the composition of the corrosion product layer and had an obvious inhibitory effect on the local corrosion of 5083 in seawater.After 16-day exposure,shallower and more sparsely distributed pits could be observed on the derusted surface of 5083 in the seawater containing phosphate,and the pitting coefficient in the seawater containing phosphate was significantly lower than that in natural seawater.The reduction of pitting tendency could be realized mainly through two ways.First,the HPO_4~(2-)adsorbed on the surface of the passive film in the early stage of corrosion and repeled the corrosive anions such as Cl~-.Second,phosphate participated in the construction of the Ca HPO_4 precipitation film,which acted as a barrier and protection.展开更多
The passivation behavior of Fe in the acidic AlCl_3-1-ethyl-3-methyl-imidazolium chloride(AlCl_3-EMIC) ionic liquid was studied by linear sweep voltammetry and chonopotentiometry. Various approaches were used to chara...The passivation behavior of Fe in the acidic AlCl_3-1-ethyl-3-methyl-imidazolium chloride(AlCl_3-EMIC) ionic liquid was studied by linear sweep voltammetry and chonopotentiometry. Various approaches were used to characterize the composition and morphology of passive film formed on the Fe electrode, such as scanning electron microscopy(SEM), Raman spectra and X-ray Photoelectron Spectroscopy(XPS). The results showed that the critical passivation potential of Fe shifted to more negative when the molar ratio of AlCl_3:EMIC changing from 2 to 1.3.A film with a light yellow color was observed on the surface of the Fe electrode after passivation. The composition of the passive film was demonstrated to be FeCl_2. The passive film was composed of particulate FeCl_2 with average diameter of about 500 nm. The formation of FeCl_2 film was attributed to the variation of the electrolyte Lewis acidity from acidic to neutral at the interface during the dissolution process of Fe. The reason caused the variation of the electrolyte acidity was discussed.展开更多
In this work,the passivity of AZ31B alloy in NaOH solutions was studied by potentiodynamic polarization,electrochemical impedance spectroscopy(EIS)and Mott-Schottky analysis.Potentiodynamic polarization results indica...In this work,the passivity of AZ31B alloy in NaOH solutions was studied by potentiodynamic polarization,electrochemical impedance spectroscopy(EIS)and Mott-Schottky analysis.Potentiodynamic polarization results indicated that decreasing NaOH concentration leads to decrease the corrosion rate of this alloy.EIS results showed that the reciprocal capacitance(1/C)of the passive film is directly proportional to its thickness which increases with decreasing NaOH concentration.Therefore,it is clear that dilute NaOH solutions offer better conditions for forming the passive films with higher protection behaviour,due to the growth of a much thicker and less defective films.The Mott-Schottky analysis revealed that the passive films displayed n-type semiconductive characteristics,where the oxygen vacancies and interstitials(over the cation vacancies)preponderated.Also,Mott-Schottky results showed that the donor densities evaluated from Mott-Schottky plots are in the range of 10^(20) cm^(−3) and decreased with decreasing NaOH concentration.展开更多
Being an exclusive construction material for lightweight rail vehicles,protection from pitting corrosion in harsh marine atmospheric environment in high humidity and Cl-ion concentration is critical for austenitic SUS...Being an exclusive construction material for lightweight rail vehicles,protection from pitting corrosion in harsh marine atmospheric environment in high humidity and Cl-ion concentration is critical for austenitic SUS 301L stainless steel(SS),especially when it inevitably suff ers from mechanical damages during post disposals.Herein,an innovative dry passivation method for austenitic SUS 301L SS was established in a closed air atmosphere at low temperature and constant pressure.The process parameters were optimized,and the passivation mechanism was explained using polarization curve,electrochemical impedance spectroscopy(EIS),X-ray photoelectron spectroscopy(XPS),and contact angle measurement.The pitting corrosion susceptibility of the passive fi lm prepared in a closed air chamber under 1.0×10^(5) Pa at 80℃ for 80 min was evaluated in 3.5%NaCl solution and exhibited higher pitting potential and corrosion resistance,lower passivity-maintaining current density,and wettability when compared with conventional nitric acid treatment.Besides,dry passivation facilitated the repairing of the surface structural defect itself and the post-processing damage,similar to the accelerated aging of fi lm.The decrease in oxygen concentration and convection-diff usion strengthened the preferential chromium oxidation to form a compact chromium-rich passive fi lm to resist the aggression of Cl-ion.展开更多
With prices for metal resources such as nickel and molybdenum soaring,there is a heightened sense of crisis concerning resource scarcity.While Type304,the most common stainless steel,offers excellent corrosion resista...With prices for metal resources such as nickel and molybdenum soaring,there is a heightened sense of crisis concerning resource scarcity.While Type304,the most common stainless steel,offers excellent corrosion resistance,its price is affected significantly by the cost of nickel because of its 8%nickel content.The stainless steel that has the same corrosion resistance as that of Type304 and does not contain nickel and molybdenum has been required.JFE Steel Corporation has developed a new 21%Cr-0.4%Cu stainless steel,the world’s first ferritic stainless steel,which offers equivalent corrosion resistance to Type304 while containing absolutely no nickel or molybdenum,two rare metals.The newly developed steel contains 21%chromium with the addition of 0.4% copper.The development of the steel is based on a new discovery that the passive films of stainless steels could be strengthened by the synergy effect of high chromium content and copper addition.Copper addition enriches the chromium content in passive films after field exposure.Newly developed 21%Cr-0.4%Cu stainless steel is adopted for many applications as a substitution for Type304,including commercial kitchenware,building materials and industrial machinery.The steel is expected to be a new standard of a ferritic stainless steel as a substitution for Type304.展开更多
Electrochemical tests and surface analysis were applied to study the corrosion behavior and passive film characteristics of three-dimensional-printed NiTi shape memory alloys fabricated by laser-powder bed fusion(LPBF...Electrochemical tests and surface analysis were applied to study the corrosion behavior and passive film characteristics of three-dimensional-printed NiTi shape memory alloys fabricated by laser-powder bed fusion(LPBF) in artificial saliva at 37.C. The passivity of L-PBF NiTi shows to be influenced by the process parameters and resulting morphological and physicochemical surface properties. The results show that the defects at the surface of L-PBF Ni Ti can promote the passivation rate in the early stages of exposure but a slowly formed passive film shows the best corrosion protection. The thickness of the passive film is positively correlated with its corrosion protective performance. The L-PBF NiTi alloy prepared at a linear energy density of 0.2 J·m^(-1) and volumetric energy density of 56 J·mm^(-3) shows the least defects and best corrosion protection. An outer Ti-rich and inner Ni-rich dense passive film could be also obtained showing higher corrosion resistance.展开更多
In actual physiological environments,bacteria can activate the immune system and release lactic acid.However,the detailed contribution of lactic acid to the passivation behavior of titanium(Ti)alloys is still unclear....In actual physiological environments,bacteria can activate the immune system and release lactic acid.However,the detailed contribution of lactic acid to the passivation behavior of titanium(Ti)alloys is still unclear.The current work investigated the in vitro passivation behavior of Ti-6Al-4V(TC4)alloys fabricated by laser powder bed fusion in Hank's solution with and without adding lactic acid.Electrochemical methods,inductively coupled plasma atomic emission spectrometer,and X-ray photoelectron spectroscopy were jointly used.Adding lactic acid decreases the corrosion resistance of samples by degrading the formed passive film.The film formed in the(lactic acid)-containing solution exhibits a higher level of oxygen vacancies and a lower thickness,attributed to the suppressed formation of Ti^(4+)transformed from Ti^(3+)and Ti^(2+).Moreover,the presence of lactic acid would increase the open circuit potential,relieve the ions release,and hinder the deposition of calcium phosphates within 24 h immersion.展开更多
In this work,the stability of passive film for long-time immersed Cu-bearing L605(L605-Cu) alloy in the phosphate buffer solution(PBS) was studied by potentiodynamic polarization and electrochemical impedance spectros...In this work,the stability of passive film for long-time immersed Cu-bearing L605(L605-Cu) alloy in the phosphate buffer solution(PBS) was studied by potentiodynamic polarization and electrochemical impedance spectroscopy.The results showed that the impedance of passive film for L605-Cu alloy experienced an initial increase and subsequent stabilization with the increase in the immersion time.In addition,the plate count method was employed to assess the antibacterial durability of L605-Cu alloy against Escherichia coli after long-time immersion.The results indicated that the antibacterial rate of L605-Cu alloy presented a declining tendency with the immersion time prolonging.X-ray photoelectron spectroscopy(XPS) was used to analyze the change of the chemical composition in the passive film on L605-Cu alloy immersed in the PBS for different time.The results showed that Cu content and its compounds in the passive film gradually increased with the immersion time prolonging,hinting declined activity of Cu ions penetrating into the passive film,which resulted in a decrease in the antibacterial performance.展开更多
This study employs advanced electrochemical and surface characterization techniques to investigate the impact of electrochemical hydrogen charging on the corrosion behavior and surface film of the Ti-6Al-4V alloy.The ...This study employs advanced electrochemical and surface characterization techniques to investigate the impact of electrochemical hydrogen charging on the corrosion behavior and surface film of the Ti-6Al-4V alloy.The findings revealed the formation ofγ-TiH andδ-TiH_(2) hydrides in the alloy after hydrogen charging.Prolonging hydrogen charging resulted in more significant degradation of the alloy microstructure,leading to deteriorated protectiveness of the surface film.This trend was further confirmed by the electrochemical measurements,which showed that the corrosion resistance of the alloy progressively worsened as the hydrogen charging time was increased.Consequently,this work provides valuable insights into the mechanisms underlying the corrosion of Ti-6Al-4V alloy under hydrogen charging conditions.展开更多
In conventional corrosion-resistant alloys,precipitation usually reduces corrosion resistance severely by weakening passive films locally.In this work,we found that the aging-treated AlCoCrFeNi_(2.1)sam-ples,which hav...In conventional corrosion-resistant alloys,precipitation usually reduces corrosion resistance severely by weakening passive films locally.In this work,we found that the aging-treated AlCoCrFeNi_(2.1)sam-ples,which have abundant nanosized L 12 and body-centered cubic(BCC)precipitates in the lamellar face-centered cubic(FCC)and B2 phases,displayed better corrosion resistance than solution-treated AlCoCrFeNi_(2.1)samples without precipitates.In the AlCoCrFeNi_(2.1)alloy,the FCC phase with L1_(2)precipi-tates and the B2 phase with BCC precipitates were protected by passive films enriched with Cr and Al elements,respectively.Moreover,the Al-rich passive film of the B2 phase was less stable than the Cr-rich passive film of the FCC phase,so B2 phase dissolved preferentially.The Cr-rich passive film of the FCC phase remained stable with the formation of Al-rich L1_(2)precipitates inside the phase because those precipitates with the size of∼5 nm were too small to affect the composition of the Cr-rich passive film.The formation of Cr-rich BCC precipitates within the B2 phase increased the content of the Al element inside the phase,improving the stability of Al-rich passive film on the B2 phase.Furthermore,BCC precip-itates with the size of∼30 nm were protected by Cr-rich passive film,which could inhibit the expansion of corrosion pits.Thus,the corrosion resistance of eutectic high-entropy alloy AlCoCrFeN 2.1 was unprece-dentedly enhanced by the precipitation of BCC precipitates.Our study could provide an attractive strategy for designing high-entropy alloys with excellent corrosion resistance and high strength.展开更多
To understand the corrosion performance of additive-manufactured Ni-based in various corrosion media during the actual engineering application environment,the corrosion properties of NiFeCrMo alloys were investigated ...To understand the corrosion performance of additive-manufactured Ni-based in various corrosion media during the actual engineering application environment,the corrosion properties of NiFeCrMo alloys were investigated in 3.5 wt.%NaCl solution,1 mol/L H2SO_(4) solution,and 1 mol/L KOH solution,using potentiodynamic polarization and electrochemical impedance spectroscopy.The electrochemical measurement results revealed that the additive-manufactured NiFeCrMo alloys have higher corrosion resistance in all three solutions,compared with the as-cast samples.The results of the scanning electron microscope confirmed that the degree of additive-manufactured NiFeCrMo alloys after potentiostatic polarization in all three solutions is less serious.X-ray photoelectron spectroscopy analysis revealed that the enhancement of the corrosion resistance for the additive-manufactured NiFeCrMo alloys is attributed to the modification of the composition of the passive films.Additive manufactured processing promotes the enrichment of the element of Cr or Mo in the passive film and it suppresses the formation of the oxidation of the element of Fe,leading to higher stability of the passive films.The reason for the higher corrosion resistance of the additive-manufactured NiFeCrMo alloys was related to the enrichment of the element of Cr,as well as the lower content of the elements of Ni and Fe near the grain boundaries,which are beneficial to forming a more compact passive film.The combined results are essential for the applications of high-strength Ni-based as structural materials in a corrosion environment.展开更多
Post-heat treatment is generally adopted in the additive manufacturing field due to its alleviation of high residual stress and modification of rapid-solidified multilevel heterogeneous microstructure,and the related ...Post-heat treatment is generally adopted in the additive manufacturing field due to its alleviation of high residual stress and modification of rapid-solidified multilevel heterogeneous microstructure,and the related performance of the heat-treated counterparts calls for a systemic investigation to build a criterion of the heat treatment procedure.In this work,we focus on the heat treatment effects on the recrystallization of the Hastelloy X alloy produced by the laser powder bed fusion(LPBF)method,and the related surface passivation of the heat-treated counterparts is meticulously assessed as well.Results show that the multilevel heterostructure for LPBF Hastelloy X alloy consists of sub-micro dislocation cell substructures with Cr/Mo elemental segregation,fine columnar grains,and periodically-distributed molten pools.After heat treatment,partially and fully recrystallized structures for LPBF Hastelloy X alloys were achieved at 1100 and 1200℃for 1 h,respectively.Furthermore,the as-built LPBF Hastelloy X alloy shows superior corrosion resistance while the heat-treated one(1100℃)exhibits the worst in the borate buffer solution.The growth of passive film exhibited a highly linear correlation with the nucleation process controlled by diffusion,and high dislocation density and low angle grain boundary decreased the diffusion coefficient of cation vacancies,augmenting the nucleation sites of the passive film and enhancing its growth rate.Moreover,the micro-galvanic effect resulting from the partially recrystallized microstructure actively facilitated the formation of inhomogeneous porous passive films,leading to the worst corrosion resistance.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51871026)the Natural Science Foundation of Zhejiang Province,China(No.LY18E010004)supported by the National Material Environmental Corrosion Infrastructure,China。
文摘The effect of microstructure and passive film on the corrosion resistance of 2507 super duplex stainless steel(SDSS)in simulated marine environment was investigated by electrochemical measurements,periodic wet–dry cyclic corrosion test,scanning Kelvin probe force microscopy,atomic force microscopy,and X-ray photoelectron spectrometry.The results show that the occupation ratio ofγphase increases with the decrease in cooling rate,whereas the content ofαphase reduces gradually.In addition,theσprecipitated phase only emerges in the annealed steel.The pitting sensitivity and corrosion rate of 2507 SDSS reduce first and then increase as the cooling rate decreases.Theσprecipitated phase drastically reduces the protective ability of the passive film and facilitates micro-galvanic corrosion of the annealed steel.For various microstructures,the pits are preferentially distributed within theσandγphases.The corrosion resistance of 2507 SDSS prepared by different cooling methods is closely related to the microstructure and structure(stability and homogeneity)of the passive film.Normalized steel shows an optimal corrosion resistance,followed by the quenched and annealed steels.
基金by the National Basic Research Program of China(2009AA03Z529)。
文摘To study the effect of free radical photocurable passivation film modified by titanate coupling agent for hot-plated aluminum-zinc plate,trimethylpropane triacrylate(TMPTA)and 2-phenoxyethyl acrylate were used as active diluents,a mixture of modified epoxy acrylate and modified polyester acrylate in a certain proportion was used as an oligomer,2-methyl-1-[4-(methylothyl)benzene]-2-morpholine acetone(907)was used as a free radical photoinitiator,isopropyl thioxanthone(ITX)was used as sensitizer,and bis(dioctyl phosphate acyl)titanate ethyltitanate acrylamide chelate(FD-812)was used as corrosion inhibitor modifier.After UV-curing,the passivation film was characterized by neutral salt spray test,electrochemical testing and other methods.The general performance of the passivation film may meet the requirements of downstream users of hot aluminum-zinc steel plate.The neutral salt spray test,electrochemical testing and microscopic surface morphology analysis of passivation film are in agreement.The introduction of titanate components may effectively promote the photocuring of free radicals.There have been few reports on the titanate coupling which is added to UV-curing coating formula.The titanate coupling agent contains acrylamide groups and terminal amine groups,acrylamide group has oligomer and crosslinking monomer,the terminal tertiary amine groups can provide hydrogen protons,reduce oxygen polymerization,and a phosphating film is formed on the surface of the metal substrate to improve the adhesion and corrosion resistance of the coating.
文摘The properties of the films formed in the electrolyte of PC/DME LiClO4 on two kinds of Carbon materials were examined by cathodic polarization measurements. The result suggested that the films on both carbon electrodes have different morphology which resulted in the different cell performance of the two carbon anodes.
文摘Passive films formed on sensitized stainless steel in sulphuric acid solutions have been studied using photoefectrochemical techniques. The results of the photocurrent measurement indicate that the passive films on sensitized stainless steel are characterised with n-type or p-type semiconductor in different potential regions. The difference in the photoelectrochemical behaviour can be interpreted assuming that the passive film is an iron-chromium oxide solid solution associated with various hydration degrees of the Cr(Ⅲ) oxides at various
文摘The surface treatment technology of hot aluminum-zinc steel plate and UV curing technology may be effectively combined in the present research. According to different light curing mechanisms, different formulations from UV curing surface treatment agents can be applied to the surface treatment of hot aluminum-zinc steel plate, mainly including 3-ethyl-3-benzoxy-methyl oxacyclobutane (TCM 104) and 3,4-epoxy-cyclohexylformic acid -3',4'-epoxy-cyclohexyl methyl ester (UVR 6110) as active diluents, high molecular weight polyfunctional oxacyclobutane as oligomer, triaryl sulfonium salt as a cationic photoinitiator, and an anthracene compound as a sensitizer. 385 nm LED lamp used as a radiation resource, the effects of the proportion of active diluent, the type and amount of photoinitiator, the amount of sensitizer, the curing temperature, and the amount of nano-SiO<sub>2</sub> on the photocuring rate were investigated by photoper-scanning differential calorimetry (Photo-DSC). The experimental results show that the system has the fastest photocuring rate under the conditions of 8:2 ratio of TCM 104 to UVR 6110, 2.5% photoinitiator, 0.6% sensitizer, 0.2% nano-SiO<sub>2</sub> additive, and 80˚C curing temperature. Based on addition of the appropriate number of various additives, the cationic photocuring surface treatment solution was prepared and further coated on the hot-dip galvalume steel plates. After curing, the passivation films were characterized by neutral salt spray test (NSST), Fourier transform infrared spectroscopy (FT-IR), electrochemical testing and other methods. The results show that the formulations could be cured at an energy of 150 mJ/cm<sup>2</sup>, and the overall performance of the passivation film could meet with the requirements of the downstream users.
基金supported by National Natural Science Foundation of China(52170074).
文摘Air nanobubbles(A-NBs)were used to inhibit the brass corrosion in circulating cooling water for the first time in the study.The results of mass loss method and electrochemical method showed that A-NBs had the obvious corrosion inhibition effect.The inhibition rate reached 52%at 35℃.The impedance and surface characterization results of corrosion samples indicated that the corrosion inhibition mechanisms of A-NBs mainly included adsorption of corrosion ions,promoting the formation of the passivation film on metal surface and the formation of the bubble layer and scale film on metal surface.A-NBs are potential excellent corrosion inhibitors.
文摘The present study investigates the mechanical and in-vitro corrosion behavior of Mg-4Zn-0.5Ca-0.8Mn alloy in optimum homogenized conditions.The optimization of the homogenization parameters has been carried out employing thermodynamic calculations and kinetic modeling.The model utilizes the inter-diffusivity of the solute elements and predicts that∼6–24 h of homogenization at 633 K effectively redistributes the elements in the Mg matrix.Based on the insights obtained from the simulations,the as-cast Mg-4Zn-0.5Ca-0.8Mn alloy was subjected to homogenization heat treatment process for 6–24h.The microstructural study through optical microscopy and scanning electron microscopy(SEM)revealed that the interconnected network of second phase precipitates substantially dissolve within 24 h,implying adequate homogenization.Moreover,fine Mg-Zn based precipitates with varied morphology and phase fractions also evolved during homogenization treatment,as confirmed through SEM and transmission electron microscopy.In the 12 h homogenized specimen,the highest fraction of uniformly dispersed fine precipitates resulted in the highest strength(∼225 MPa).On the other hand,a substantial disruption in coarse precipitate network and lower aspect ratio of fine Mg-Zn precipitates led to the highest ductility(∼8%)in this specimen.In the 24 h homogenized specimen,the ductility reduced marginally owing to higher aspect ratio of fine precipitates.The immersion and electrochemical tests(viz.,potentiodynamic polarization and electrochemical impedance spectroscopy)carried out in Hank’s solution revealed that the 24 h homogenized specimen exhibits the best corrosion properties.The least fraction of Ca_(2)Mg_(6)Zn_(3)phase with maximum disruption in interconnectivity,in combination with a small fraction of fine equilibrium MgZn_(2)precipitates,resulted in suppression of localized corrosion in this specimen.This promotes the formation of the most stable and compact product layer over the specimen,resulting in the highest corrosion resistance.
文摘The corrosion behaviour of bronze alloy prepared by equal channel angular pressing(ECAP) was investigated in 3.5 wt. % Na Cl solution.Immersion corrosion tests and different electrochemical techniques were carried out. The results showed that ECAPed bronze samples exhibited higher corrosion resistance compared with the as-cast alloy and the passive current density decreased with increasing number of passes. Moreover,the morphology of alloys indicated that the corrosion damage on the surface of ECAPed bronze was smooth and uniform while the as-cast alloy suffered from selective corrosion.
基金supported by the National Natural Science Foundation of China (No. U1706221)。
文摘As a material with good corrosion resistance,5083 aluminum alloy has a great application prospect in marine environment.In this work,the corrosion characteristics of 5083 aluminum alloy in seawater containing phosphate were investigated with Potentiodynamic Polarization,Electrochemical Impedance Spectroscopy (EIS),Scanning Electron Microscope (SEM),Energy Dispersive Spectroscopy Analysis (EDSA),X-ray Photoelectron Spectroscopy (XPS) and Laser Confocal Microscope.The results indicated that the effects of phosphate in seawater were two-fold.Firstly,phosphate slightly accelerated the corrosion of 5083 in seawater in the early stage of corrosion.HPO_4~(2-)competed with OH~-in the adsorption process on the alloy surface,which weakened the contact between OH~-and Al~(3+)near the interface of the alloy,and inhibited the formation as well as the self-repair of the passive film,thus accelerating the activation dissolution process.Compared with the natural seawater,the charge transfer resistance of 5083 in the seawater containing phosphate decreased faster during the early stage of corrosion,and the corrosion current density i_(corr) was higher in seawater containing phosphate.On the other hand,the addition of phosphate would not affect the cluster distribution of the second phase of 5083 in seawater,but it changed the composition of the corrosion product layer and had an obvious inhibitory effect on the local corrosion of 5083 in seawater.After 16-day exposure,shallower and more sparsely distributed pits could be observed on the derusted surface of 5083 in the seawater containing phosphate,and the pitting coefficient in the seawater containing phosphate was significantly lower than that in natural seawater.The reduction of pitting tendency could be realized mainly through two ways.First,the HPO_4~(2-)adsorbed on the surface of the passive film in the early stage of corrosion and repeled the corrosive anions such as Cl~-.Second,phosphate participated in the construction of the Ca HPO_4 precipitation film,which acted as a barrier and protection.
基金the National Natural Science Foundation of China(No.51271166)
文摘The passivation behavior of Fe in the acidic AlCl_3-1-ethyl-3-methyl-imidazolium chloride(AlCl_3-EMIC) ionic liquid was studied by linear sweep voltammetry and chonopotentiometry. Various approaches were used to characterize the composition and morphology of passive film formed on the Fe electrode, such as scanning electron microscopy(SEM), Raman spectra and X-ray Photoelectron Spectroscopy(XPS). The results showed that the critical passivation potential of Fe shifted to more negative when the molar ratio of AlCl_3:EMIC changing from 2 to 1.3.A film with a light yellow color was observed on the surface of the Fe electrode after passivation. The composition of the passive film was demonstrated to be FeCl_2. The passive film was composed of particulate FeCl_2 with average diameter of about 500 nm. The formation of FeCl_2 film was attributed to the variation of the electrolyte Lewis acidity from acidic to neutral at the interface during the dissolution process of Fe. The reason caused the variation of the electrolyte acidity was discussed.
文摘In this work,the passivity of AZ31B alloy in NaOH solutions was studied by potentiodynamic polarization,electrochemical impedance spectroscopy(EIS)and Mott-Schottky analysis.Potentiodynamic polarization results indicated that decreasing NaOH concentration leads to decrease the corrosion rate of this alloy.EIS results showed that the reciprocal capacitance(1/C)of the passive film is directly proportional to its thickness which increases with decreasing NaOH concentration.Therefore,it is clear that dilute NaOH solutions offer better conditions for forming the passive films with higher protection behaviour,due to the growth of a much thicker and less defective films.The Mott-Schottky analysis revealed that the passive films displayed n-type semiconductive characteristics,where the oxygen vacancies and interstitials(over the cation vacancies)preponderated.Also,Mott-Schottky results showed that the donor densities evaluated from Mott-Schottky plots are in the range of 10^(20) cm^(−3) and decreased with decreasing NaOH concentration.
基金Supported by the CRRC Changchun Railway Vehicles Co.,Ltd.(No.GYHB(12)-01-00-014(067))the Natural Science Foundation of Shandong Province,China(No.ZR2020MB080)。
文摘Being an exclusive construction material for lightweight rail vehicles,protection from pitting corrosion in harsh marine atmospheric environment in high humidity and Cl-ion concentration is critical for austenitic SUS 301L stainless steel(SS),especially when it inevitably suff ers from mechanical damages during post disposals.Herein,an innovative dry passivation method for austenitic SUS 301L SS was established in a closed air atmosphere at low temperature and constant pressure.The process parameters were optimized,and the passivation mechanism was explained using polarization curve,electrochemical impedance spectroscopy(EIS),X-ray photoelectron spectroscopy(XPS),and contact angle measurement.The pitting corrosion susceptibility of the passive fi lm prepared in a closed air chamber under 1.0×10^(5) Pa at 80℃ for 80 min was evaluated in 3.5%NaCl solution and exhibited higher pitting potential and corrosion resistance,lower passivity-maintaining current density,and wettability when compared with conventional nitric acid treatment.Besides,dry passivation facilitated the repairing of the surface structural defect itself and the post-processing damage,similar to the accelerated aging of fi lm.The decrease in oxygen concentration and convection-diff usion strengthened the preferential chromium oxidation to form a compact chromium-rich passive fi lm to resist the aggression of Cl-ion.
文摘With prices for metal resources such as nickel and molybdenum soaring,there is a heightened sense of crisis concerning resource scarcity.While Type304,the most common stainless steel,offers excellent corrosion resistance,its price is affected significantly by the cost of nickel because of its 8%nickel content.The stainless steel that has the same corrosion resistance as that of Type304 and does not contain nickel and molybdenum has been required.JFE Steel Corporation has developed a new 21%Cr-0.4%Cu stainless steel,the world’s first ferritic stainless steel,which offers equivalent corrosion resistance to Type304 while containing absolutely no nickel or molybdenum,two rare metals.The newly developed steel contains 21%chromium with the addition of 0.4% copper.The development of the steel is based on a new discovery that the passive films of stainless steels could be strengthened by the synergy effect of high chromium content and copper addition.Copper addition enriches the chromium content in passive films after field exposure.Newly developed 21%Cr-0.4%Cu stainless steel is adopted for many applications as a substitution for Type304,including commercial kitchenware,building materials and industrial machinery.The steel is expected to be a new standard of a ferritic stainless steel as a substitution for Type304.
基金financially supported by the financial support from the International Postdoctoral Exchange Fellowship Program 2019 by the Office of China Postdoctoral Council (No. 20190086)the support from the Russian Science Foundation Grant (No. 19-79-30002)。
文摘Electrochemical tests and surface analysis were applied to study the corrosion behavior and passive film characteristics of three-dimensional-printed NiTi shape memory alloys fabricated by laser-powder bed fusion(LPBF) in artificial saliva at 37.C. The passivity of L-PBF NiTi shows to be influenced by the process parameters and resulting morphological and physicochemical surface properties. The results show that the defects at the surface of L-PBF Ni Ti can promote the passivation rate in the early stages of exposure but a slowly formed passive film shows the best corrosion protection. The thickness of the passive film is positively correlated with its corrosion protective performance. The L-PBF NiTi alloy prepared at a linear energy density of 0.2 J·m^(-1) and volumetric energy density of 56 J·mm^(-3) shows the least defects and best corrosion protection. An outer Ti-rich and inner Ni-rich dense passive film could be also obtained showing higher corrosion resistance.
基金The authors acknowledge the Fundamental Research Program of Jiangsu Province(BK20201000)the Australian Research Council through the Discovery Project(DP110101653,DP130103592)+1 种基金the Basic and Applied Basic Research Foundation of Guangdong Province,China(2022A1515140123,2021A1515110729)the Foshan(Southern China)Institute for New Materials(2021AYF25017).The authors are grateful to Jinling Zhu.
文摘In actual physiological environments,bacteria can activate the immune system and release lactic acid.However,the detailed contribution of lactic acid to the passivation behavior of titanium(Ti)alloys is still unclear.The current work investigated the in vitro passivation behavior of Ti-6Al-4V(TC4)alloys fabricated by laser powder bed fusion in Hank's solution with and without adding lactic acid.Electrochemical methods,inductively coupled plasma atomic emission spectrometer,and X-ray photoelectron spectroscopy were jointly used.Adding lactic acid decreases the corrosion resistance of samples by degrading the formed passive film.The film formed in the(lactic acid)-containing solution exhibits a higher level of oxygen vacancies and a lower thickness,attributed to the suppressed formation of Ti^(4+)transformed from Ti^(3+)and Ti^(2+).Moreover,the presence of lactic acid would increase the open circuit potential,relieve the ions release,and hinder the deposition of calcium phosphates within 24 h immersion.
基金financially supported by the National Natural Science Foundation of China (Nos.51771199, 51631009 and 51501188)the National Key Research and Development Program (No.2016YFB0300205)。
文摘In this work,the stability of passive film for long-time immersed Cu-bearing L605(L605-Cu) alloy in the phosphate buffer solution(PBS) was studied by potentiodynamic polarization and electrochemical impedance spectroscopy.The results showed that the impedance of passive film for L605-Cu alloy experienced an initial increase and subsequent stabilization with the increase in the immersion time.In addition,the plate count method was employed to assess the antibacterial durability of L605-Cu alloy against Escherichia coli after long-time immersion.The results indicated that the antibacterial rate of L605-Cu alloy presented a declining tendency with the immersion time prolonging.X-ray photoelectron spectroscopy(XPS) was used to analyze the change of the chemical composition in the passive film on L605-Cu alloy immersed in the PBS for different time.The results showed that Cu content and its compounds in the passive film gradually increased with the immersion time prolonging,hinting declined activity of Cu ions penetrating into the passive film,which resulted in a decrease in the antibacterial performance.
基金Supported by National Natural Science Foundation of China(Grant Nos.52001142,52005228,51801218,51911530211,51905110)Young Scientists Sponsorship Program by CAST(Grant No.2022QNRC001).
文摘This study employs advanced electrochemical and surface characterization techniques to investigate the impact of electrochemical hydrogen charging on the corrosion behavior and surface film of the Ti-6Al-4V alloy.The findings revealed the formation ofγ-TiH andδ-TiH_(2) hydrides in the alloy after hydrogen charging.Prolonging hydrogen charging resulted in more significant degradation of the alloy microstructure,leading to deteriorated protectiveness of the surface film.This trend was further confirmed by the electrochemical measurements,which showed that the corrosion resistance of the alloy progressively worsened as the hydrogen charging time was increased.Consequently,this work provides valuable insights into the mechanisms underlying the corrosion of Ti-6Al-4V alloy under hydrogen charging conditions.
基金This work was financially supported by the Natural Science Foundation of Hebei Province(No.E2020202009)the Tianjin Science and Technology Plan Project(No.20JCQNJC00900)+3 种基金the Science and Technology Project of Hebei Education Department(No.QN2020150)the National Natural Science Foundation of China(No.52101011)the Central Funds Guiding the Local Science and Technology Development of Hebei Province(No.226Z1001G)the Central Funds Guiding the Local Science and Technology Development of Hebei Province(No.226Z1012G).
文摘In conventional corrosion-resistant alloys,precipitation usually reduces corrosion resistance severely by weakening passive films locally.In this work,we found that the aging-treated AlCoCrFeNi_(2.1)sam-ples,which have abundant nanosized L 12 and body-centered cubic(BCC)precipitates in the lamellar face-centered cubic(FCC)and B2 phases,displayed better corrosion resistance than solution-treated AlCoCrFeNi_(2.1)samples without precipitates.In the AlCoCrFeNi_(2.1)alloy,the FCC phase with L1_(2)precipi-tates and the B2 phase with BCC precipitates were protected by passive films enriched with Cr and Al elements,respectively.Moreover,the Al-rich passive film of the B2 phase was less stable than the Cr-rich passive film of the FCC phase,so B2 phase dissolved preferentially.The Cr-rich passive film of the FCC phase remained stable with the formation of Al-rich L1_(2)precipitates inside the phase because those precipitates with the size of∼5 nm were too small to affect the composition of the Cr-rich passive film.The formation of Cr-rich BCC precipitates within the B2 phase increased the content of the Al element inside the phase,improving the stability of Al-rich passive film on the B2 phase.Furthermore,BCC precip-itates with the size of∼30 nm were protected by Cr-rich passive film,which could inhibit the expansion of corrosion pits.Thus,the corrosion resistance of eutectic high-entropy alloy AlCoCrFeN 2.1 was unprece-dentedly enhanced by the precipitation of BCC precipitates.Our study could provide an attractive strategy for designing high-entropy alloys with excellent corrosion resistance and high strength.
基金supported by the National Natural Science Foundation of China(51901086).
文摘To understand the corrosion performance of additive-manufactured Ni-based in various corrosion media during the actual engineering application environment,the corrosion properties of NiFeCrMo alloys were investigated in 3.5 wt.%NaCl solution,1 mol/L H2SO_(4) solution,and 1 mol/L KOH solution,using potentiodynamic polarization and electrochemical impedance spectroscopy.The electrochemical measurement results revealed that the additive-manufactured NiFeCrMo alloys have higher corrosion resistance in all three solutions,compared with the as-cast samples.The results of the scanning electron microscope confirmed that the degree of additive-manufactured NiFeCrMo alloys after potentiostatic polarization in all three solutions is less serious.X-ray photoelectron spectroscopy analysis revealed that the enhancement of the corrosion resistance for the additive-manufactured NiFeCrMo alloys is attributed to the modification of the composition of the passive films.Additive manufactured processing promotes the enrichment of the element of Cr or Mo in the passive film and it suppresses the formation of the oxidation of the element of Fe,leading to higher stability of the passive films.The reason for the higher corrosion resistance of the additive-manufactured NiFeCrMo alloys was related to the enrichment of the element of Cr,as well as the lower content of the elements of Ni and Fe near the grain boundaries,which are beneficial to forming a more compact passive film.The combined results are essential for the applications of high-strength Ni-based as structural materials in a corrosion environment.
基金the National Science Fund for Distinguished Young Scholars(No.52125102)the China Postdoctoral Science Foundation(Nos.2022TQ0203 and 2022M722047)+1 种基金Fundamental Research Funds for the Central Universities(No.FRF-TP-2021-02C2)Shanghai Technical Barriers to Trade(No.2021TBT004).
文摘Post-heat treatment is generally adopted in the additive manufacturing field due to its alleviation of high residual stress and modification of rapid-solidified multilevel heterogeneous microstructure,and the related performance of the heat-treated counterparts calls for a systemic investigation to build a criterion of the heat treatment procedure.In this work,we focus on the heat treatment effects on the recrystallization of the Hastelloy X alloy produced by the laser powder bed fusion(LPBF)method,and the related surface passivation of the heat-treated counterparts is meticulously assessed as well.Results show that the multilevel heterostructure for LPBF Hastelloy X alloy consists of sub-micro dislocation cell substructures with Cr/Mo elemental segregation,fine columnar grains,and periodically-distributed molten pools.After heat treatment,partially and fully recrystallized structures for LPBF Hastelloy X alloys were achieved at 1100 and 1200℃for 1 h,respectively.Furthermore,the as-built LPBF Hastelloy X alloy shows superior corrosion resistance while the heat-treated one(1100℃)exhibits the worst in the borate buffer solution.The growth of passive film exhibited a highly linear correlation with the nucleation process controlled by diffusion,and high dislocation density and low angle grain boundary decreased the diffusion coefficient of cation vacancies,augmenting the nucleation sites of the passive film and enhancing its growth rate.Moreover,the micro-galvanic effect resulting from the partially recrystallized microstructure actively facilitated the formation of inhomogeneous porous passive films,leading to the worst corrosion resistance.
