This study presents a novel approach to improving the anticorrosive performance of AZ31 Mg alloy by exploiting the role of the hydration reaction to induce interactions between Quinolin-8-ol(8HQ)molecules and the poro...This study presents a novel approach to improving the anticorrosive performance of AZ31 Mg alloy by exploiting the role of the hydration reaction to induce interactions between Quinolin-8-ol(8HQ)molecules and the porous MgO layer formed via plasma electrolytic oxidation(PEO).The AZ31 Mg alloy,initially coated with a PEO layer,underwent a dipping treatment in an ethanolic solution of 0.05 M 8HQ at 50℃ for 3 h.The results were compared with those from a different procedure where the PEO layer was subjected to a hydration reaction for 2 h at 90℃ before immersion in the 8HQ solution under the same conditions.The hydration treatment played a crucial role by converting MgO to Mg(OH)_(2),significantly enhancing the surface reactivity.This transformation introduced hydroxyl groups(−OH)on the surface,which facilitated donor-acceptor interactions with the electron-accepting sites on 8HQ molecules.The calculated binding energy(Ebinding)from DFT indicated that the interaction energy of 8HQ with Mg(OH)_(2) was lower compared to 8HQ with MgO,suggesting easier adsorption of 8HQ molecules on the hydrated surface.This,combined with the increased number of active sites and enhanced surface area,allowed for extensive surface coverage by 8HQ,leading to the formation of a stable,flake-like protective layer that sealed the majority of pores on the PEO layer.DFT calculations further suggested that the hydration treatment provided multiple active sites,enabling effective contact with 8HQ and rapid electron transfer,creating ideal conditions for charge-transfer-induced physical and chemical bonding.This study shows that hydration and 8HQ treatments significantly enhance the corrosion resistance of Mg alloys,highlighting their potential for advanced anticorrosive coatings.展开更多
In this study,laser-assisted plasma electrolytic oxidation(Laser/PEO)coating was prepared on AZ31B magnesium alloy for corrosion protection,due to insufficient corrosion protection caused by the inherent defects,crack...In this study,laser-assisted plasma electrolytic oxidation(Laser/PEO)coating was prepared on AZ31B magnesium alloy for corrosion protection,due to insufficient corrosion protection caused by the inherent defects,cracks and poor quality of PEO coatings.The plasma discharge evolution,morphological characteristics,elemental composition during coating growth were characterized by high-speed camera,SEM,EDX,XRD and XPS,respectively.Meanwhile,Mott Schottky(M-S)curves,potentiodynamic polarization(PDP)curves and electrochemical impedance spectroscopy(EIS)tests characterized the oxygen vacancy defects and corrosion resistance of the coatings.The results demonstrated that laser-assisted irradiation not only induced plasma discharge on the anode surface,but also limited the plasma discharge size in the post-processing stage,which significantly increased the proportion of corrosion-resistant phase Mg_(2)SiO_(4)(the proportion of Mg_(2)SiO_(4)increased from 23.70%to 39.22%),thickness and density in the coating,and obviously reduced the oxygen vacancy defects and microcracks in the coating.As a result,the corrosion resistance of the Laser/PEO coating(9.29(±0.76)×10^(-7)A·cm^(-2))was further enhanced in comparation with the PEO coating(3.06(±0.19)×10^(-6) A·cm^(-2)).展开更多
The corrosion resistance of magnesium alloys is a significant concern in industries seeking to use these materials for lightweight structures.Plasma electrolytic oxidation(PEO)is a process that forms a ceramic oxide f...The corrosion resistance of magnesium alloys is a significant concern in industries seeking to use these materials for lightweight structures.Plasma electrolytic oxidation(PEO)is a process that forms a ceramic oxide film on Mg alloy surfaces,effectively enhancing their corrosion performance in the short term.In this regard,optimizing PEO process parameters is crucial for creating a stable oxide layer.An improved level of corrosion resistance is ensured by applying superhydrophobic coating(SHC)on top of the PEO layer to prevent moisture infiltration,creating air pockets on the surface.Various methods are employed to fabricate SHC on Mg alloys,including techniques like electrophoretic deposition(EPD),Hydrothermal(HT),dip,and spray coating.The synergistic combination of PEO and SHC coatings has demonstrated encouraging outcomes in enhancing the corrosion performance of Mg alloys.This study offers an extensive overview of recent progress in the preparation,characterization,and corrosion behavior of Mg alloys by employing PEO coatings and SHC treatment processes.展开更多
A novel type of microcapsule-encapsulated corrosion inhibitor was prepared in a water-based solution with a pH range of 7-8,and it was applied to the composite organic coating of magnesium alloy plasma electrolytic ox...A novel type of microcapsule-encapsulated corrosion inhibitor was prepared in a water-based solution with a pH range of 7-8,and it was applied to the composite organic coating of magnesium alloy plasma electrolytic oxidation to enhance its corrosion resistance and self-healing properties.The morphology,chemical composition,structure,and functional properties of the composite coating were investigated by scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared spectroscopy(FTIR),polarization curve,alternating current impedance,and salt immersion test.The experimental results showed that,after immersion in a 3.5 wt%NaCl solution for 12 h,the coating could effectively protect AZ91D from corrosion.When the coating was damaged,the exposed alloy surface would release metal ions in the corrosive environment and react with the corrosion inhibitor 8-hydroxyquinoline to form a Mg(8-HQ)_(2) chelate,exhibiting significant self-healing behavior.The study results demonstrate the broad application prospects of microcapsule technology in the coating field,providing new ideas for the development of efficient anti-corrosion coatings.展开更多
Plasma electrolytic oxidation(PEO)coatings were prepared on Al−Mg laminated macro composites(LMCs)using both unipolar and bipolar waveforms in an appropriate electrolyte for both aluminum and magnesium alloys.The tech...Plasma electrolytic oxidation(PEO)coatings were prepared on Al−Mg laminated macro composites(LMCs)using both unipolar and bipolar waveforms in an appropriate electrolyte for both aluminum and magnesium alloys.The techniques of FESEM/EDS,grazing incident beam X-ray diffraction(GIXRD),and electrochemical methods of potentiodynamic polarization and electrochemical impedance spectroscopy(EIS)were used to characterize the coatings.The results revealed that the coatings produced using the bipolar waveform exhibited lower porosity and higher thickness than those produced using the unipolar one.The corrosion performance of the specimens’cut edge was investigated using EIS after 1,8,and 12 h of immersion in a 3.5 wt.%NaCl solution.It was observed that the coating produced using the bipolar waveform demonstrated the highest corrosion resistance after 12 h of immersion,with an estimated corrosion resistance of 5.64 kΩ·cm^(2),which was approximately 3 times higher than that of the unipolar coating.Notably,no signs of galvanic corrosion were observed in the LMCs,and only minor corrosion attacks were observed on the magnesium layer in some areas.展开更多
To enhance the long-term corrosion resistance of the plasma electrolytic oxidation(PEO)coating on the magnesium(Mg)alloy,an inorganic salt combined with corrosion inhibitors was used for posttreatment of the coating.I...To enhance the long-term corrosion resistance of the plasma electrolytic oxidation(PEO)coating on the magnesium(Mg)alloy,an inorganic salt combined with corrosion inhibitors was used for posttreatment of the coating.In this study,the corrosion performance of PEO-coated AM50 Mg was significantly improved by loading sodium lauryl sulfonate(SDS)and sodium dodecyl benzene sulf-onate into Ba(NO_(3))_(2) post-sealing solutions.Scanning electron microscopy,X-ray photoelectron spectroscopy,X-ray diffraction,Fourier transform infrared spectrometer,and ultraviolet-visible analyses showed that the inhibitors enhanced the incorporation of BaO_(2) into PEO coatings.Electrochemical impedance showed that post-sealing in Ba(NO_(3))_(2)/SDS treatment enhanced corrosion resistance by three orders of magnitude.The total impedance value remained at 926Ω·cm^(2)after immersing in a 0.5wt%NaCl solution for 768 h.A salt spray test for 40 days did not show any obvious region of corrosion,proving excellent post-sealing by Ba(NO_(3))_(2)/SDS treatment.The corrosion resistance of the coating was enhanced through the synergistic effect of BaO2 pore sealing and SDS adsorption.展开更多
In the present research,the NaF assisted plasma electrolytic oxidation(PEO)is designed to fabricate the high-content ZnO nanoparti-cles doped coating on AZ31B alloy.The microstructure,phase constituents and corrosion ...In the present research,the NaF assisted plasma electrolytic oxidation(PEO)is designed to fabricate the high-content ZnO nanoparti-cles doped coating on AZ31B alloy.The microstructure,phase constituents and corrosion behavior of the PEO coatings are investigated systematically.The results reveal that the introduction of NaF promotes the formation of MgF2 nanophases in the passivation layer on Mg alloy,decreasing the breakdown voltage and discharge voltage.As a result,the continuous arcing caused by high discharge voltage is alleviated.With the increasing of NaF content,the Zn content in the PEO coating is enhanced and the pore size in the coating is decreased correspondingly.Due to the high-content ZnO doping,the PEO coating protected AZ31B alloy demonstrates the better corrosion resistance.Compared with the bare AZ31B alloy,the high-content ZnO doped PEO coated sample shows an increased corrosion potential from-1.465 V to-1.008 V,a decreased corrosion current density from 3.043×10^(-5) A·cm^(-2) to 3.960×10^(-8) A·cm^(-2) and an increased charge transfer resistance from 1.213×10^(2) ohm·cm^(2) to 2.598×10^(5) ohm·cm^(2).Besides,the high-content ZnO doped PEO coated sample also has the excellent corrosion resistance in salt solution,exhibiting no obvious corrosion after more than 2000 h neutral salt spraying and 28 days’immersion testing.The improved corrosion resistance can be ascribed to the relative uniform distribution of ZnO in PEO coating which can transform to Zn(OH)2 and form a continuous protective layer along the corrosion interface.展开更多
The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation(PEO)coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate(PTO)using pulsed...The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation(PEO)coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate(PTO)using pulsed bipolar waveforms with various cathodic duty cycles and cathodic current densities.The coatings were characterized by SEM,EDS,and XRD.EIS was applied to investigate the electrochemical properties.It was observed that the increase of cathodic duty cycle and cathodic current density from 20%and 6 A/dm^(2) to 40%and 12 A/dm^(2) enhances the growth rate of the inner layer from 0.22 to 0.75μm/min.Adding PTO into the bath showed a fortifying effect on influence of the cathodic pulse and the mentioned change of cathodic pulse parameters,resulting in an increase of the inner layer growth rate from 0.25 to 1.10μm/min.Based on EDS analysis,Si and Ti were incorporated dominantly in the upper parts of the coatings.XRD technique merely detectedγ-Al_(2)O_(3),and there were no detectable peaks related to Ti and Si compounds.However,the EIS results confirmed that the incorporation of Ti^(4+)into alumina changed the electronic properties of the coating.The coatings obtained from the bath containing PTO using the bipolar waveforms with a cathodic duty cycle of 40%and current density values higher than 6 A/dm^(2) showed highly appropriate electrochemical behavior during 240 d of immersion due to an efficient repairing mechanism.Regarding the effects of studied parameters on the coating properties,the roles of cathodic pulse parameters and PTO in the PEO process were highlighted.展开更多
Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density o...Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.展开更多
The formation processes of a composite ceramic coating on AM50 magnesium alloy prepared by plasma electrolytic oxidation （PEO） in a K 2 ZrF 6 electrolyte solution were studied by scanning electron microscope （SEM）...The formation processes of a composite ceramic coating on AM50 magnesium alloy prepared by plasma electrolytic oxidation （PEO） in a K 2 ZrF 6 electrolyte solution were studied by scanning electron microscope （SEM） and energy dispersive X-ray spectroscope （EDX）. Electrochemical impedance spectroscopy （EIS） tests were used to study the variation of the corrosion resistance of the coating during the PEO treatment. The results show that the coating formed on Mg alloy is mainly composed of MgO and MgF 2 when the applied voltage is lower than the sparking voltage, and zirconium oxides start to be deposited on Mg substrate after the potential exceeding the sparking voltage. The corrosion resistance of the coating increases with increasing the applied voltage.展开更多
The plasma electrolytic oxidation（PEO） coatings on zircaloy？4 alloy were prepared in silicate,phosphate and pyrophosphate electrolyte systems or their combination by DC current regime.The proper processing paramete...The plasma electrolytic oxidation（PEO） coatings on zircaloy？4 alloy were prepared in silicate,phosphate and pyrophosphate electrolyte systems or their combination by DC current regime.The proper processing parameters were determined and the coatings were evaluated by electrochemistry technique,micro-hardness,SEM and XRD.The results show that the coating prepared in pure silicate system is uneven and after the addition of phosphate solution,the homogeneity of the coating is still poor.The coating prepared in pure pyrophosphate electrolyte system is homogeneous,but its hardness value is low.After the addition of silicate into the pyrophosphate electrolytic system,both the uniformity and hardness of the coating are improved.The XRD results show that the phase compositions are m-ZrO2 and t-ZrO2,the addition of silicate is beneficial to the formation of t-ZrO2.The results of polarization curves show that the coatings prepared in pyrophosphate and the mixture of pyrophosphate and silicate have better corrosion resistance.展开更多
In this study,a phosphate-based conversion coating(PCC)was applied as a precursor before forming silicate-fluoride(SiF)and silicate-phosphate-fluoride(SiPF)based flash-plasma electrolytic oxidation(Flash-PEO)coatings ...In this study,a phosphate-based conversion coating(PCC)was applied as a precursor before forming silicate-fluoride(SiF)and silicate-phosphate-fluoride(SiPF)based flash-plasma electrolytic oxidation(Flash-PEO)coatings on AZ31B magnesium alloy.The main novelty is the successful incorporation of calcium,zinc,manganese and phosphate species into the Flash-PEO coatings via a precursor layer rather than using the electrolyte.The precursor also led to longer lasting and more intense discharges during the PEO process,resulting in increased pore size.Corrosion studies revealed similar short-term performance for all coatings,with impedance modulus at low frequencies above 10^(7)Ωcm^(2),and slightly better performance for the SiPF-based coating.Nonetheless,the enlarged pores in the PEO coatings functionalized with the PCC precursor compromised the effectiveness of self-healing mechanisms by creating diffusion pathways for corrosive species,leading to earlier failure.These phenomena were effectively monitored by recording the open circuit potential during immersion in 0.5 wt.%NaCl solution.In summary,this study demonstrates that conversion coatings are a viable option for the functionalization of PEO coatings on magnesium alloys,as they allow for the incorporation of cationic and other species.However,it is crucial to maintain a small pore size to facilitate effective blockage through self-healing mechanisms.展开更多
This study presents a novel photocatalytic system exploiting the unique properties of ZrO_(2) and its integration with layered double hydroxide(LDH)films on porous coatings produced via plasma electrolytic oxidation(PE...This study presents a novel photocatalytic system exploiting the unique properties of ZrO_(2) and its integration with layered double hydroxide(LDH)films on porous coatings produced via plasma electrolytic oxidation(PEO).Herein,CoFe-LDHfilms were created on the porous surface of PEO-coated AZ31 Mg alloy using a hydrothermal treatment in cobalt and iron nitrate solutions,followed by a secondary hydrothermal process in a ZrO_(2) solution for 10 h at 70℃.The impact of ZrO_(2) on the morphological,compositional,and photocatalytic performance was then compared to the case where ZrO_(2) nanoparticles were electrophoretically incorporated into the porous PEO coating.Characterization results revealed that the ZrO_(2)-modified LDH coatings exhibited a dispersedflake-like structure with an increased surface area,a reduced band gap energy of 3.14 eV,and enhanced electron-hole separation.Experimental results demonstrated an outstanding 99.8%degradation of indigo carmine within 15 mins,with remarkable multi-cycle stability overfive consecutive cycles without significant performance decline.This system demonstrates faster degradation rates and greater durability compared to previously reported catalysts,underscoring its potential for effective and sustainable environmental remediation.The synergistic integration of ZrO_(2),LDH,and PEO highlights a promising strategy for wastewater treatment,particularly for the removal of persistent organic dyes like indigo carmine.展开更多
Novel neutral electrolytes were designed to substantially decrease porosity and increase barrier property of plasma electrolytic oxidation(PEO)coating on AM50 Mg surface.Presence of additives was effective in tuning c...Novel neutral electrolytes were designed to substantially decrease porosity and increase barrier property of plasma electrolytic oxidation(PEO)coating on AM50 Mg surface.Presence of additives was effective in tuning coating microstructure and composition,leading to significantly enhanced corrosion and wear properties.50%improvement in fatigue limit was detected for the optimized coating compared to conventional PEO coating.The low-porosity coating remained uncorroded after performing salt spray test for 1 month,and exposure 1 year in harsh South China Sea environment.This can be new strategy to evaluate coating lifespan and promote wide range of applications for Mg alloy.展开更多
Plasma electrolytic oxidation is a well-known technique for surface modification of biomedical magnesium alloys,with good corrosion protection and the ability to produce biocompatible and bioactive coatings.In this st...Plasma electrolytic oxidation is a well-known technique for surface modification of biomedical magnesium alloys,with good corrosion protection and the ability to produce biocompatible and bioactive coatings.In this study,calcium-phosphate coatings were produced on WE43 magnesium alloy for use,as orthopedic implants.Coating formation was prepared using different oxidation parameters with various duty ratios(DR)of 15,25 and 50%and current ratios(R)-2 or 1.6.Application of R with excess cathodic current(R>1)in processes with DR≥25%allowed attaining the soft-sparking regime(SSR)that resulted in thicker oxide coatings with higher degree of crystallinity compared to the films obtained without SSR.The results of the corrosion tests contributed to a noticeable improvement in the corrosion resistance of the magnesium alloy.Optimization of the oxidation parameters allowed the selection of the variants with the most favorable degradation behavior over the tested immersion period,indicating a successful modification of the magnesium alloy surface to obtain an implant biomaterial capable of providing controlled degradation.Furthermore,biological evaluation of the produced coatings showed that the proposed surface modifications significantly reduced the cytotoxic effects observed in direct contact with the material while still maintaining the cell proliferation-promoting effects of the material eluents.展开更多
Electrolyte selection for Plasma Electrolytic Oxidation(PEO)of magnesium is important as this determines composition,morphology and properties of resultant coatings that are urgently sought after for protection of Mg ...Electrolyte selection for Plasma Electrolytic Oxidation(PEO)of magnesium is important as this determines composition,morphology and properties of resultant coatings that are urgently sought after for protection of Mg alloys from corrosion and wear in harsh environments.However,electrolyte design is often performed heuristically,which hampers the development and optimisation of new PEO processes.Here,we attempt to achieve a mechanistic understanding of electrochemical and microstructural aspects of anodic films evolution at the prebreakdown stages of PEO treatments of magnesium in aqueous alkaline solutions of NaAlO_(2),Na_(3)PO_(4),Na F and Na_(2)SiO_(3).Systematic studies have shown that magnesium self-passivation by MgO/Mg(OH)_(2)can be compromised by both chemical and mechanical instabilities developed due to side effects of anodic reactions.Stable initiation of PEO process requires maintaining surface passivity in a wide range of p H,which can be achieved only by combining self-depositing passivators with those binding dissolved magnesium into insoluble compounds.展开更多
Plasma electrolytic oxidation(PEO)processing of light metals has been established for decades and is in increasing industrial use,even as an alternative surface treatment to produce multifunctional coatings with envir...Plasma electrolytic oxidation(PEO)processing of light metals has been established for decades and is in increasing industrial use,even as an alternative surface treatment to produce multifunctional coatings with environmental-friendly processing concept.One of the benefits of PEO processing claimed already a couple of years ago was the ability to treat dissimilar metal joints,which can obviously improve the surface homogeneity and stability at the interface of the dissimilar components,especially impeding the galvanic corrosion due to the different electrochemical properties of each component.However,the progress and breakthrough develop slowly especially for the macro scales due to the much larger gap between each component.This literature review firstly demonstrates the still low number of studies reporting successful PEO treatment of material combination such as Mg/Al,Mg/Ti,Al/Ti and scarcely light metal combinations with steel.The main issues and challenges to performing PEO processing on the macroscale dissimilar weldments were stated.On the other hand,dissimilar metal joints also widely exist in micrometer scale in alloys and metal matrix composites(MMCs).Moreover,there is a huge knowledge base on PEO treatment of such multiphase substrates.PEO processing of such complicated mixed microstructures is reviewed as well to reveal the basic problems.To some certain degree,these PEO-related studies on alloys and MMCs can be good examples to have an insight into the coating formation mechanism on macro-scaled dissimilar metal joints.Conclusions are drawn from the micro-to macroscale.Finally,critical access to the problems is given and possible solutions and reaming limitations are discussed.展开更多
Plasma electrolytic oxidation of a cast A356 aluminum alloy was carried out in aluminate electrolytes to develop wear and corrosion resistant coatings. Different concentrations of 2, 16 and 24 g/L NaAlO2 solutions and...Plasma electrolytic oxidation of a cast A356 aluminum alloy was carried out in aluminate electrolytes to develop wear and corrosion resistant coatings. Different concentrations of 2, 16 and 24 g/L NaAlO2 solutions and a silicate electrolyte （for comparison） were employed for the investigation. Wear performance and corrosion resistance of the coatings were evaluated by WC （tungsten carbide） ball-on-flat dry sliding tests and electrochemical methods, respectively. The results show that the coating formed for a short duration of 480 s in 24 g/L NaAlO2 solution generated the best protection. The coating sustained 30 N load for sliding time of 1800 s, showing very low wear rate of -4.5×10^-7 mm3/（N· m）. A low corrosion current density of -8.81×10^-9 A/cm2 was also recorded. Despite low α-Al2O3 content of the coating, the compact and nearly single layer nature of the coating guaranteed the excellent performances.展开更多
Plasma Electrolyte Oxidation(PEO)process has increasingly been employed to improve magnesium surface properties by fabrication of an MgO-based coating.Originating from conventional anodizing procedures,this high-volta...Plasma Electrolyte Oxidation(PEO)process has increasingly been employed to improve magnesium surface properties by fabrication of an MgO-based coating.Originating from conventional anodizing procedures,this high-voltage process produces an adhesive ceramic film on the surface.The present article provides a comprehensive review around mechanisms of PEO coatings fabrication and their different properties.Due to complexity of PEO coatings formation,a complete explanation regarding fabrication mechanisms of PEO coatings has not yet been proposed;however,the most important advancements in the field of fabrication mechanisms of PEO coatings were gathered in this work.Mechanisms of PEO coatings fabrication on magnesium were reviewed considering voltage–time plots,optical spectrometry,acoustic emission spectrometry and electronic properties of the ceramic film.Afterwards,the coatings properties,affecting parameters and improvement strategies were discussed.In addition,corrosion resistance of coatings,important factors in corrosion resistance and methods for corrosion resistance improvement were considered.Tribological properties(important factors and improvement methods)of coatings were also studied.Since magnesium and its alloys are broadly used in biological applications,the biological properties of PEO coatings,important factors in their biological performance and existing methods for improvement of coatings were explained.Addition of ceramic based nanoparticles and formation of nanocomposite coatings may considerably influence properties of plasma electrolyte oxidation coatings.Nanocomposite coatings properties and nanoparticles adsorption mechanisms were included in a separate sector.Another method to improve coatings properties is formation of hybrid coatings on PEO coatings which was discussed in the end.展开更多
Plasma electrolytic oxidation(PEO),a promising surface treatment method to improve the corrosion and wear resistance of magnesium and its alloys,operates at high voltages,resulting in a relatively high energy cost.To ...Plasma electrolytic oxidation(PEO),a promising surface treatment method to improve the corrosion and wear resistance of magnesium and its alloys,operates at high voltages,resulting in a relatively high energy cost.To make the PEO process more economically viable,its energy efficiency needs to be improved.This study investigates the growth behaviour and microstructural characteristics of low-energy PEO coatings on an AM50 magnesium alloy in a concentrated electrolyte containing sodium tetraborate.The surface morphology of the coatings was different from typical PEO coating morphologies and a large voltage oscillation was observed during treatment.Using different characterisation techniques,and based on a micro-discharge model,a correlation was made between the voltage-time behaviour,microdischarge characteristics and the composition and microstructure of the coated samples.The results suggest electrolyte chemistry can somewhat control discharge behaviour,which plays an important role in PEO coating growth.展开更多
基金supported by the National Research Foundation of Korea(NRF)funded by the Korean government(MSIT)(No.2022R1A2C1006743).
文摘This study presents a novel approach to improving the anticorrosive performance of AZ31 Mg alloy by exploiting the role of the hydration reaction to induce interactions between Quinolin-8-ol(8HQ)molecules and the porous MgO layer formed via plasma electrolytic oxidation(PEO).The AZ31 Mg alloy,initially coated with a PEO layer,underwent a dipping treatment in an ethanolic solution of 0.05 M 8HQ at 50℃ for 3 h.The results were compared with those from a different procedure where the PEO layer was subjected to a hydration reaction for 2 h at 90℃ before immersion in the 8HQ solution under the same conditions.The hydration treatment played a crucial role by converting MgO to Mg(OH)_(2),significantly enhancing the surface reactivity.This transformation introduced hydroxyl groups(−OH)on the surface,which facilitated donor-acceptor interactions with the electron-accepting sites on 8HQ molecules.The calculated binding energy(Ebinding)from DFT indicated that the interaction energy of 8HQ with Mg(OH)_(2) was lower compared to 8HQ with MgO,suggesting easier adsorption of 8HQ molecules on the hydrated surface.This,combined with the increased number of active sites and enhanced surface area,allowed for extensive surface coverage by 8HQ,leading to the formation of a stable,flake-like protective layer that sealed the majority of pores on the PEO layer.DFT calculations further suggested that the hydration treatment provided multiple active sites,enabling effective contact with 8HQ and rapid electron transfer,creating ideal conditions for charge-transfer-induced physical and chemical bonding.This study shows that hydration and 8HQ treatments significantly enhance the corrosion resistance of Mg alloys,highlighting their potential for advanced anticorrosive coatings.
基金The National Natural Science Foundation of China(U2130122,U22A20199,and 51975533)Natural Science Foundation of Zhejiang Province(LGJ22E050002)+1 种基金Equipment pre-research joint fund project of the Ministry of Education(8091B022215)China Postdoctoral Science Foundation(2023M733147)funded this research.
文摘In this study,laser-assisted plasma electrolytic oxidation(Laser/PEO)coating was prepared on AZ31B magnesium alloy for corrosion protection,due to insufficient corrosion protection caused by the inherent defects,cracks and poor quality of PEO coatings.The plasma discharge evolution,morphological characteristics,elemental composition during coating growth were characterized by high-speed camera,SEM,EDX,XRD and XPS,respectively.Meanwhile,Mott Schottky(M-S)curves,potentiodynamic polarization(PDP)curves and electrochemical impedance spectroscopy(EIS)tests characterized the oxygen vacancy defects and corrosion resistance of the coatings.The results demonstrated that laser-assisted irradiation not only induced plasma discharge on the anode surface,but also limited the plasma discharge size in the post-processing stage,which significantly increased the proportion of corrosion-resistant phase Mg_(2)SiO_(4)(the proportion of Mg_(2)SiO_(4)increased from 23.70%to 39.22%),thickness and density in the coating,and obviously reduced the oxygen vacancy defects and microcracks in the coating.As a result,the corrosion resistance of the Laser/PEO coating(9.29(±0.76)×10^(-7)A·cm^(-2))was further enhanced in comparation with the PEO coating(3.06(±0.19)×10^(-6) A·cm^(-2)).
文摘The corrosion resistance of magnesium alloys is a significant concern in industries seeking to use these materials for lightweight structures.Plasma electrolytic oxidation(PEO)is a process that forms a ceramic oxide film on Mg alloy surfaces,effectively enhancing their corrosion performance in the short term.In this regard,optimizing PEO process parameters is crucial for creating a stable oxide layer.An improved level of corrosion resistance is ensured by applying superhydrophobic coating(SHC)on top of the PEO layer to prevent moisture infiltration,creating air pockets on the surface.Various methods are employed to fabricate SHC on Mg alloys,including techniques like electrophoretic deposition(EPD),Hydrothermal(HT),dip,and spray coating.The synergistic combination of PEO and SHC coatings has demonstrated encouraging outcomes in enhancing the corrosion performance of Mg alloys.This study offers an extensive overview of recent progress in the preparation,characterization,and corrosion behavior of Mg alloys by employing PEO coatings and SHC treatment processes.
基金Funded by the National Natural Science Foundation of China(No.52271066)Basic Research and Innovation Project for Vehicle Power+1 种基金Key Project of"Two-Chain Integration"in Shaanxi Province(No.2023-LL-QY-33-3)Xi'an Key Laboratory of Corrosion Protection and Functional Coating Technology for Military and Civil Light Alloy and Key Project of Shaanxi Natural Science Foundation Research Program(No.2021JZ-54)。
文摘A novel type of microcapsule-encapsulated corrosion inhibitor was prepared in a water-based solution with a pH range of 7-8,and it was applied to the composite organic coating of magnesium alloy plasma electrolytic oxidation to enhance its corrosion resistance and self-healing properties.The morphology,chemical composition,structure,and functional properties of the composite coating were investigated by scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),Fourier transform infrared spectroscopy(FTIR),polarization curve,alternating current impedance,and salt immersion test.The experimental results showed that,after immersion in a 3.5 wt%NaCl solution for 12 h,the coating could effectively protect AZ91D from corrosion.When the coating was damaged,the exposed alloy surface would release metal ions in the corrosive environment and react with the corrosion inhibitor 8-hydroxyquinoline to form a Mg(8-HQ)_(2) chelate,exhibiting significant self-healing behavior.The study results demonstrate the broad application prospects of microcapsule technology in the coating field,providing new ideas for the development of efficient anti-corrosion coatings.
文摘Plasma electrolytic oxidation(PEO)coatings were prepared on Al−Mg laminated macro composites(LMCs)using both unipolar and bipolar waveforms in an appropriate electrolyte for both aluminum and magnesium alloys.The techniques of FESEM/EDS,grazing incident beam X-ray diffraction(GIXRD),and electrochemical methods of potentiodynamic polarization and electrochemical impedance spectroscopy(EIS)were used to characterize the coatings.The results revealed that the coatings produced using the bipolar waveform exhibited lower porosity and higher thickness than those produced using the unipolar one.The corrosion performance of the specimens’cut edge was investigated using EIS after 1,8,and 12 h of immersion in a 3.5 wt.%NaCl solution.It was observed that the coating produced using the bipolar waveform demonstrated the highest corrosion resistance after 12 h of immersion,with an estimated corrosion resistance of 5.64 kΩ·cm^(2),which was approximately 3 times higher than that of the unipolar coating.Notably,no signs of galvanic corrosion were observed in the LMCs,and only minor corrosion attacks were observed on the magnesium layer in some areas.
基金financial support by the National Natural Science Foundation of China(No.52071067)Shenyang Young and Middle-aged Science and Technology Innovation Talent Support Program,China(No.RC231178)+1 种基金Natural Science Foundation of Liaoning Province,China(No.2022-YGJC-16)the Fundamental Research Funds for the Central Universities,China(No.N2302019).
文摘To enhance the long-term corrosion resistance of the plasma electrolytic oxidation(PEO)coating on the magnesium(Mg)alloy,an inorganic salt combined with corrosion inhibitors was used for posttreatment of the coating.In this study,the corrosion performance of PEO-coated AM50 Mg was significantly improved by loading sodium lauryl sulfonate(SDS)and sodium dodecyl benzene sulf-onate into Ba(NO_(3))_(2) post-sealing solutions.Scanning electron microscopy,X-ray photoelectron spectroscopy,X-ray diffraction,Fourier transform infrared spectrometer,and ultraviolet-visible analyses showed that the inhibitors enhanced the incorporation of BaO_(2) into PEO coatings.Electrochemical impedance showed that post-sealing in Ba(NO_(3))_(2)/SDS treatment enhanced corrosion resistance by three orders of magnitude.The total impedance value remained at 926Ω·cm^(2)after immersing in a 0.5wt%NaCl solution for 768 h.A salt spray test for 40 days did not show any obvious region of corrosion,proving excellent post-sealing by Ba(NO_(3))_(2)/SDS treatment.The corrosion resistance of the coating was enhanced through the synergistic effect of BaO2 pore sealing and SDS adsorption.
基金supported by the 2022 Shenzhen sustainable supporting funds for colleges and universities(20220810143642004)Shenzhen Basic Research Project(JCYJ20200109144608205 and JCYJ20210324120001003)+5 种基金Peking University Shenzhen Graduate School Research Startup Fund of Introducing Talent(No.1270110273)Shenzhen postdoctoral research fund project after outbound(No.2129933651)Shenzhen-Hong Kong Research and Development Fund(No.SGDX20201103095406024)City University of Hong Kong Strategic Research Grants(SRG)(Nos.7005264 and 7005505)Guangdong-Hong Kong Technology Cooperation Funding Scheme(TCFS)(No.GHP/085/18SZ)IER Foundation(IERF2020001 and IERF2019002).
文摘In the present research,the NaF assisted plasma electrolytic oxidation(PEO)is designed to fabricate the high-content ZnO nanoparti-cles doped coating on AZ31B alloy.The microstructure,phase constituents and corrosion behavior of the PEO coatings are investigated systematically.The results reveal that the introduction of NaF promotes the formation of MgF2 nanophases in the passivation layer on Mg alloy,decreasing the breakdown voltage and discharge voltage.As a result,the continuous arcing caused by high discharge voltage is alleviated.With the increasing of NaF content,the Zn content in the PEO coating is enhanced and the pore size in the coating is decreased correspondingly.Due to the high-content ZnO doping,the PEO coating protected AZ31B alloy demonstrates the better corrosion resistance.Compared with the bare AZ31B alloy,the high-content ZnO doped PEO coated sample shows an increased corrosion potential from-1.465 V to-1.008 V,a decreased corrosion current density from 3.043×10^(-5) A·cm^(-2) to 3.960×10^(-8) A·cm^(-2) and an increased charge transfer resistance from 1.213×10^(2) ohm·cm^(2) to 2.598×10^(5) ohm·cm^(2).Besides,the high-content ZnO doped PEO coated sample also has the excellent corrosion resistance in salt solution,exhibiting no obvious corrosion after more than 2000 h neutral salt spraying and 28 days’immersion testing.The improved corrosion resistance can be ascribed to the relative uniform distribution of ZnO in PEO coating which can transform to Zn(OH)2 and form a continuous protective layer along the corrosion interface.
文摘The influence of cathodic pulse parameters was evaluated on plasma electrolytic oxidation(PEO)coatings grown on 7075 aluminum alloy in a silicate-based electrolyte containing potassium titanyl oxalate(PTO)using pulsed bipolar waveforms with various cathodic duty cycles and cathodic current densities.The coatings were characterized by SEM,EDS,and XRD.EIS was applied to investigate the electrochemical properties.It was observed that the increase of cathodic duty cycle and cathodic current density from 20%and 6 A/dm^(2) to 40%and 12 A/dm^(2) enhances the growth rate of the inner layer from 0.22 to 0.75μm/min.Adding PTO into the bath showed a fortifying effect on influence of the cathodic pulse and the mentioned change of cathodic pulse parameters,resulting in an increase of the inner layer growth rate from 0.25 to 1.10μm/min.Based on EDS analysis,Si and Ti were incorporated dominantly in the upper parts of the coatings.XRD technique merely detectedγ-Al_(2)O_(3),and there were no detectable peaks related to Ti and Si compounds.However,the EIS results confirmed that the incorporation of Ti^(4+)into alumina changed the electronic properties of the coating.The coatings obtained from the bath containing PTO using the bipolar waveforms with a cathodic duty cycle of 40%and current density values higher than 6 A/dm^(2) showed highly appropriate electrochemical behavior during 240 d of immersion due to an efficient repairing mechanism.Regarding the effects of studied parameters on the coating properties,the roles of cathodic pulse parameters and PTO in the PEO process were highlighted.
基金Project(51371039)supported by the National Natural Science Foundation of China
文摘Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.
基金Project(2007CB613705)supported by the National Basic Research Program of ChinaProject(50901082)supported by the NationalNatural Science Foundation of China
文摘The formation processes of a composite ceramic coating on AM50 magnesium alloy prepared by plasma electrolytic oxidation （PEO） in a K 2 ZrF 6 electrolyte solution were studied by scanning electron microscope （SEM） and energy dispersive X-ray spectroscope （EDX）. Electrochemical impedance spectroscopy （EIS） tests were used to study the variation of the corrosion resistance of the coating during the PEO treatment. The results show that the coating formed on Mg alloy is mainly composed of MgO and MgF 2 when the applied voltage is lower than the sparking voltage, and zirconium oxides start to be deposited on Mg substrate after the potential exceeding the sparking voltage. The corrosion resistance of the coating increases with increasing the applied voltage.
基金Project (51071066) supported by by the National Natural Science Foundation of ChinaProject (531107040029) supported by the Fundamental Research Fund for the Central Universities,ChinaProject supported by the Development of Youth Teachers of Hunan University,China
文摘The plasma electrolytic oxidation（PEO） coatings on zircaloy？4 alloy were prepared in silicate,phosphate and pyrophosphate electrolyte systems or their combination by DC current regime.The proper processing parameters were determined and the coatings were evaluated by electrochemistry technique,micro-hardness,SEM and XRD.The results show that the coating prepared in pure silicate system is uneven and after the addition of phosphate solution,the homogeneity of the coating is still poor.The coating prepared in pure pyrophosphate electrolyte system is homogeneous,but its hardness value is low.After the addition of silicate into the pyrophosphate electrolytic system,both the uniformity and hardness of the coating are improved.The XRD results show that the phase compositions are m-ZrO2 and t-ZrO2,the addition of silicate is beneficial to the formation of t-ZrO2.The results of polarization curves show that the coatings prepared in pyrophosphate and the mixture of pyrophosphate and silicate have better corrosion resistance.
基金support of the PID2021-124341OB-C22/AEI/10.13039/501100011033/FEDER,UE(MICIU)J.M.Vega also acknowledges the Grant RYC2021-034384-I funded by MICIU/AEI/10.13039/501100011033 and by“European Union Next Generation EU/PRTR”.
文摘In this study,a phosphate-based conversion coating(PCC)was applied as a precursor before forming silicate-fluoride(SiF)and silicate-phosphate-fluoride(SiPF)based flash-plasma electrolytic oxidation(Flash-PEO)coatings on AZ31B magnesium alloy.The main novelty is the successful incorporation of calcium,zinc,manganese and phosphate species into the Flash-PEO coatings via a precursor layer rather than using the electrolyte.The precursor also led to longer lasting and more intense discharges during the PEO process,resulting in increased pore size.Corrosion studies revealed similar short-term performance for all coatings,with impedance modulus at low frequencies above 10^(7)Ωcm^(2),and slightly better performance for the SiPF-based coating.Nonetheless,the enlarged pores in the PEO coatings functionalized with the PCC precursor compromised the effectiveness of self-healing mechanisms by creating diffusion pathways for corrosive species,leading to earlier failure.These phenomena were effectively monitored by recording the open circuit potential during immersion in 0.5 wt.%NaCl solution.In summary,this study demonstrates that conversion coatings are a viable option for the functionalization of PEO coatings on magnesium alloys,as they allow for the incorporation of cationic and other species.However,it is crucial to maintain a small pore size to facilitate effective blockage through self-healing mechanisms.
基金supported by the National Research Foundation of Korea(NRF)funded by the Korean government(MSIT)(No.2022R1A2C1006743).
文摘This study presents a novel photocatalytic system exploiting the unique properties of ZrO_(2) and its integration with layered double hydroxide(LDH)films on porous coatings produced via plasma electrolytic oxidation(PEO).Herein,CoFe-LDHfilms were created on the porous surface of PEO-coated AZ31 Mg alloy using a hydrothermal treatment in cobalt and iron nitrate solutions,followed by a secondary hydrothermal process in a ZrO_(2) solution for 10 h at 70℃.The impact of ZrO_(2) on the morphological,compositional,and photocatalytic performance was then compared to the case where ZrO_(2) nanoparticles were electrophoretically incorporated into the porous PEO coating.Characterization results revealed that the ZrO_(2)-modified LDH coatings exhibited a dispersedflake-like structure with an increased surface area,a reduced band gap energy of 3.14 eV,and enhanced electron-hole separation.Experimental results demonstrated an outstanding 99.8%degradation of indigo carmine within 15 mins,with remarkable multi-cycle stability overfive consecutive cycles without significant performance decline.This system demonstrates faster degradation rates and greater durability compared to previously reported catalysts,underscoring its potential for effective and sustainable environmental remediation.The synergistic integration of ZrO_(2),LDH,and PEO highlights a promising strategy for wastewater treatment,particularly for the removal of persistent organic dyes like indigo carmine.
基金supported by LiaoNing Revitalization Talents Program(XLYC2403026)Shenyang Young and Middle-aged Science and Technology Innovation Talent Support Program(No.RC231178)the Fundamental Research Funds for the Central Universities(No.N2302019).
文摘Novel neutral electrolytes were designed to substantially decrease porosity and increase barrier property of plasma electrolytic oxidation(PEO)coating on AM50 Mg surface.Presence of additives was effective in tuning coating microstructure and composition,leading to significantly enhanced corrosion and wear properties.50%improvement in fatigue limit was detected for the optimized coating compared to conventional PEO coating.The low-porosity coating remained uncorroded after performing salt spray test for 1 month,and exposure 1 year in harsh South China Sea environment.This can be new strategy to evaluate coating lifespan and promote wide range of applications for Mg alloy.
基金funded by Silesian University of Technology,no.07/020/BKM24/0104.
文摘Plasma electrolytic oxidation is a well-known technique for surface modification of biomedical magnesium alloys,with good corrosion protection and the ability to produce biocompatible and bioactive coatings.In this study,calcium-phosphate coatings were produced on WE43 magnesium alloy for use,as orthopedic implants.Coating formation was prepared using different oxidation parameters with various duty ratios(DR)of 15,25 and 50%and current ratios(R)-2 or 1.6.Application of R with excess cathodic current(R>1)in processes with DR≥25%allowed attaining the soft-sparking regime(SSR)that resulted in thicker oxide coatings with higher degree of crystallinity compared to the films obtained without SSR.The results of the corrosion tests contributed to a noticeable improvement in the corrosion resistance of the magnesium alloy.Optimization of the oxidation parameters allowed the selection of the variants with the most favorable degradation behavior over the tested immersion period,indicating a successful modification of the magnesium alloy surface to obtain an implant biomaterial capable of providing controlled degradation.Furthermore,biological evaluation of the produced coatings showed that the proposed surface modifications significantly reduced the cytotoxic effects observed in direct contact with the material while still maintaining the cell proliferation-promoting effects of the material eluents.
基金supported by the UK EPSRC(grant EP/T024607/1,‘Coat IN’)provided by the Henry Royce Institute for Advanced Materials,funded through the UK EPSRC grants EP/R00661X/1,EP/S019367/1,EP/P025021/1 and EP/P025498/1support from the University of Manchester and Chinese Scholarship Council for his Ph D studies。
文摘Electrolyte selection for Plasma Electrolytic Oxidation(PEO)of magnesium is important as this determines composition,morphology and properties of resultant coatings that are urgently sought after for protection of Mg alloys from corrosion and wear in harsh environments.However,electrolyte design is often performed heuristically,which hampers the development and optimisation of new PEO processes.Here,we attempt to achieve a mechanistic understanding of electrochemical and microstructural aspects of anodic films evolution at the prebreakdown stages of PEO treatments of magnesium in aqueous alkaline solutions of NaAlO_(2),Na_(3)PO_(4),Na F and Na_(2)SiO_(3).Systematic studies have shown that magnesium self-passivation by MgO/Mg(OH)_(2)can be compromised by both chemical and mechanical instabilities developed due to side effects of anodic reactions.Stable initiation of PEO process requires maintaining surface passivity in a wide range of p H,which can be achieved only by combining self-depositing passivators with those binding dissolved magnesium into insoluble compounds.
基金the China Scholarship Council(No.201708510113)for fellowship and funding.
文摘Plasma electrolytic oxidation(PEO)processing of light metals has been established for decades and is in increasing industrial use,even as an alternative surface treatment to produce multifunctional coatings with environmental-friendly processing concept.One of the benefits of PEO processing claimed already a couple of years ago was the ability to treat dissimilar metal joints,which can obviously improve the surface homogeneity and stability at the interface of the dissimilar components,especially impeding the galvanic corrosion due to the different electrochemical properties of each component.However,the progress and breakthrough develop slowly especially for the macro scales due to the much larger gap between each component.This literature review firstly demonstrates the still low number of studies reporting successful PEO treatment of material combination such as Mg/Al,Mg/Ti,Al/Ti and scarcely light metal combinations with steel.The main issues and challenges to performing PEO processing on the macroscale dissimilar weldments were stated.On the other hand,dissimilar metal joints also widely exist in micrometer scale in alloys and metal matrix composites(MMCs).Moreover,there is a huge knowledge base on PEO treatment of such multiphase substrates.PEO processing of such complicated mixed microstructures is reviewed as well to reveal the basic problems.To some certain degree,these PEO-related studies on alloys and MMCs can be good examples to have an insight into the coating formation mechanism on macro-scaled dissimilar metal joints.Conclusions are drawn from the micro-to macroscale.Finally,critical access to the problems is given and possible solutions and reaming limitations are discussed.
基金Projects(51071066,51671084)supported by the National Natural Science Foundation of ChinaProject(NCET-12-0172)supported by the Program for New Century Excellent Talents in University,Ministry of Education,China
文摘Plasma electrolytic oxidation of a cast A356 aluminum alloy was carried out in aluminate electrolytes to develop wear and corrosion resistant coatings. Different concentrations of 2, 16 and 24 g/L NaAlO2 solutions and a silicate electrolyte （for comparison） were employed for the investigation. Wear performance and corrosion resistance of the coatings were evaluated by WC （tungsten carbide） ball-on-flat dry sliding tests and electrochemical methods, respectively. The results show that the coating formed for a short duration of 480 s in 24 g/L NaAlO2 solution generated the best protection. The coating sustained 30 N load for sliding time of 1800 s, showing very low wear rate of -4.5×10^-7 mm3/（N· m）. A low corrosion current density of -8.81×10^-9 A/cm2 was also recorded. Despite low α-Al2O3 content of the coating, the compact and nearly single layer nature of the coating guaranteed the excellent performances.
文摘Plasma Electrolyte Oxidation(PEO)process has increasingly been employed to improve magnesium surface properties by fabrication of an MgO-based coating.Originating from conventional anodizing procedures,this high-voltage process produces an adhesive ceramic film on the surface.The present article provides a comprehensive review around mechanisms of PEO coatings fabrication and their different properties.Due to complexity of PEO coatings formation,a complete explanation regarding fabrication mechanisms of PEO coatings has not yet been proposed;however,the most important advancements in the field of fabrication mechanisms of PEO coatings were gathered in this work.Mechanisms of PEO coatings fabrication on magnesium were reviewed considering voltage–time plots,optical spectrometry,acoustic emission spectrometry and electronic properties of the ceramic film.Afterwards,the coatings properties,affecting parameters and improvement strategies were discussed.In addition,corrosion resistance of coatings,important factors in corrosion resistance and methods for corrosion resistance improvement were considered.Tribological properties(important factors and improvement methods)of coatings were also studied.Since magnesium and its alloys are broadly used in biological applications,the biological properties of PEO coatings,important factors in their biological performance and existing methods for improvement of coatings were explained.Addition of ceramic based nanoparticles and formation of nanocomposite coatings may considerably influence properties of plasma electrolyte oxidation coatings.Nanocomposite coatings properties and nanoparticles adsorption mechanisms were included in a separate sector.Another method to improve coatings properties is formation of hybrid coatings on PEO coatings which was discussed in the end.
基金supported by Natural Science and En-gineering Research Council of Canada(NSERC)grant.
文摘Plasma electrolytic oxidation(PEO),a promising surface treatment method to improve the corrosion and wear resistance of magnesium and its alloys,operates at high voltages,resulting in a relatively high energy cost.To make the PEO process more economically viable,its energy efficiency needs to be improved.This study investigates the growth behaviour and microstructural characteristics of low-energy PEO coatings on an AM50 magnesium alloy in a concentrated electrolyte containing sodium tetraborate.The surface morphology of the coatings was different from typical PEO coating morphologies and a large voltage oscillation was observed during treatment.Using different characterisation techniques,and based on a micro-discharge model,a correlation was made between the voltage-time behaviour,microdischarge characteristics and the composition and microstructure of the coated samples.The results suggest electrolyte chemistry can somewhat control discharge behaviour,which plays an important role in PEO coating growth.
