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
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
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) 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
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
Based on orthogonal experiments,the effects of voltage,frequency,duty ratio and their interactions on the thickness and corrosion resistance of coatings prepared by plasma electrolytic oxidation(PEO)on aluminum in an ...Based on orthogonal experiments,the effects of voltage,frequency,duty ratio and their interactions on the thickness and corrosion resistance of coatings prepared by plasma electrolytic oxidation(PEO)on aluminum in an alkaline silicate-containing electrolyte were investigated.The thicknesses of these coatings were obtained by measuring their cross-section using Image J software.Their corrosion resistances were evaluated in HCl and NaCl media through spot test and electrochemical test.The results show that the experimental design of this study is the key to investigate the interactions among these electrical parameters.Additionally,not only each independent factor,but also their interactions exhibit a remarkable influence on the coatings.The combination of high voltage,low frequency and large duty ratio significantly increases the coating thickness and content of the corrosion resistance phase,and thus improves the corrosion resistance of the coating in HNO3 medium.Conversely,the coating possessing the densest microstructure and best corrosion resistance in NaCl medium is obtained when low voltage and high frequency match with a small duty ratio.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
The plasma electrolytic oxidation(PEO)procedure is utilized in order to amend the surface properties of Mg and its alloys.This procedure creates a ceramic coating on the surface applying high-voltage.The presence of d...The plasma electrolytic oxidation(PEO)procedure is utilized in order to amend the surface properties of Mg and its alloys.This procedure creates a ceramic coating on the surface applying high-voltage.The presence of deep pores and porosities in the surface that affect the corrosion resistance of the coatings is one of the PEO procedure limitations.One of the useful methods to decrease porosities of coating and improve its final properties is changing electrolyte conditions based on the presence of micro-and nanoparticles.The present paper reviews the mechanisms of particle adsorption and composition in PEO thin films in addition to the effect of particle addition on the microstructure,composition and corrosion behavior of coatings that were applied on magnesium alloys.展开更多
The growth kinetics of PEO coatings on AZ31 and AZ91 magnesium alloys were studied and correlated with their structure,compositions(phase and elemental)and corrosion resistance.It was established that the coatings hav...The growth kinetics of PEO coatings on AZ31 and AZ91 magnesium alloys were studied and correlated with their structure,compositions(phase and elemental)and corrosion resistance.It was established that the coatings have a two-(outer and anodic)or three-layer structure(outer,inner and anodic)depending on the treatment time.Briefly,at short treatment time only an anodic layer and outer layer exists.Growth of the outer PEO layer takes place due to the micro discharges,which occur in vertical pores and voids with spherical cross-section.If the time is increasing,and electrolyte inside of the pores is heating-up,etching of the Mg substrate and oxide film becomes more dominant and horizontal pores in the interface between coating and metal are formed.In the pores new anodic layer will form and at this time the formation of the third inner layer starts.The growth of the inner layer happens via the anodic film as a result of micro discharge ignition in the horizontal pores,accompanied by formation of plasma in numerous micro-voids of this layer.The coatings formed on AZ91 alloy are denser,than those on AZ31,which is related to the difference in the rates of inner layer growth and dissolving of oxides which are located at the bottom of the horizontal pores.Because of the lower Al content,the AZ31 substrate itself and the also the oxide films are less stable and tend to dissolve at a higher rate compared to AZ91.Thus,it was demonstrated that a good corrosion resistance of the coatings was only obtained on AZ91 and if the average thickness of the coating is around 50μm,correlating with the formation of a sufficiently dense inner laye-Knowing this mechanism,a new two-step treatment was suggested,combining the standard PEO treatment with a subsequent PEO process in an electrolyte supporting the inner film formation.The concept was successfully applied and a further improved corrosion resistance was obtained compared to the single stage PEO process.This improvement of corrosion resistance was related to the better sealing of porosity and formation of a denser inner layer.展开更多
In order to improve the wear and corrosion resistance of AZ31 magnesium alloy,a magnetron-sputtered Al layer with a thickness of 11μm was firstly applied on the alloy,and then treated by plasma electrolytic oxidation...In order to improve the wear and corrosion resistance of AZ31 magnesium alloy,a magnetron-sputtered Al layer with a thickness of 11μm was firstly applied on the alloy,and then treated by plasma electrolytic oxidation(PEO)in an aluminate and silicate electrolytes,respectively.The performance of PEO coatings was investigated by dry sliding wear and electrochemical corrosion tests.The aluminate coating exhibits excellent wear resistance under both 10 and 20 N loads.The silicate coating only shows low wear rate under 10 N,but it was destroyed under 20 N.Corrosion tests show that the Al layer after magnetron sputtering treatment alone cannot afford good protection to the Mg substrate.However,the duplex layer of PEO/Al can significantly improve the corrosion resistance of AZ31 alloy.Electrochemical tests show that the aluminate and silicate coatings have corrosion current densities of-1.6×10^(-6) and-1.1×10^(-6) A/cm^(2),respectively,which are two orders lower than that of the un-coated AZ31 alloy.However,immersion tests and electrochemical impedance spectroscopy(EIS)show that the aluminate coating exhibits better long-term corrosion protection than silicate coating.展开更多
As an efficient surface modification approach,the plasma electrolytic oxidation(PEO)technique can boost the capability of wear protection in Mg and its alloys by applying a hard and thick ceramic coating.In this proce...As an efficient surface modification approach,the plasma electrolytic oxidation(PEO)technique can boost the capability of wear protection in Mg and its alloys by applying a hard and thick ceramic coating.In this procedure,more efficient protection can be acquired via adding additives(in the form of particle,powder,sheet,etc.)into solutions and producing composite coatings.These additives result in more efficient protection against wear via getting stuck in the cracks and pores of coatings and rising the thickness,hardness,and diminishing the porosity size and content.The efficiency of each additive can be changed owing to its intrinsic properties like melting point,size,participation type(reactive,partly reactive,or inert)and potential of zeta.In this review,the effects of distinct additives in nano-and micro-scale size on wear behavior of PEO coatings on Mg and its alloys is going to be reviewed.展开更多
In order to improve the osseointegration and antibacterial activity of titanium alloys,micro/nano-structured ceramic coatings doped with antibacterial element F were prepared by plasma electrolytic oxidation(PEO)proce...In order to improve the osseointegration and antibacterial activity of titanium alloys,micro/nano-structured ceramic coatings doped with antibacterial element F were prepared by plasma electrolytic oxidation(PEO)process on Ti6Al4V alloy in NaF electrolyte.The influence of NaF concentration(0.15-0.50 mol/L)on the PEO process,microstructure,phase composition,corrosion resistance and thickness of the coatings was investigated using scanning/transmission electron microscopy,energy dispersive spectroscopy,atomic force microscopy,X-ray diffractometer,and potentiodynamic polarization.The results demonstrated that Ti6Al4V alloy had low PEO voltage(less than 200 V)in NaF electrolyte,which decreased further as the NaF concentration increased.A micro/nano-structured coating with 10-15μm pits and 200-800 nm pores was formed in NaF electrolyte;the morphology was different from the typical pancake structure obtained with other electrolytes.The coating formed in NaF electrolyte had low surface roughness and was thin(<4μm).The NaF concentration had a small effect on the phase transition from metastable anatase phase to stable rutile phase,but greatly affected the corrosion resistance.In general,as the NaF concentration increased,the surface roughness,phase(anatase and rutile)contents,corrosion resistance,and thickness of the coating first increased and then decreased,reaching the maximum values at 0.25 mol/L NaF.展开更多
Magnesium has been known as an appropriate biological material on account of its good biocompatibility and biodegradability properties in addition to advantageous mechanical properties.Mg and its alloys are of poor co...Magnesium has been known as an appropriate biological material on account of its good biocompatibility and biodegradability properties in addition to advantageous mechanical properties.Mg and its alloys are of poor corrosion resistance.Its high corrosion rate leads to its quick decomposition in the corrosive ambiance and as a result weakening its mechanical properties and before it is repaired,it will vanish.The corrosion and degradation rate must be controlled in the body to advance the usage of Mg and its alloys as implants.Different techniques have been utilized to boost biological properties.Plasma electrolytic oxidation(PEO)can provide porous and biocompatible coatings for implants among various techniques.Biodegradable implants are generally supposed to show enough corrosion resistance and mechanical integrity in the body environment.Much research has been carried out in order to produce PEO coatings containing calcium phosphate compounds.Calcium phosphates are really similar to bone mineral composition and present great biocompatibility.The present study deals with the usage of calcium phosphates as biocompatible coatings applied on Mg and its alloys to study the properties and control the corrosion rate.展开更多
Plasma electrolytic oxidation（PEO） coatings on AZ31 magnesium（Mg） alloy were developed using the aqueous solution with alkaline silicate and sodium hydroxide as a base electrolyte system.The effects of cerium（Ce...Plasma electrolytic oxidation（PEO） coatings on AZ31 magnesium（Mg） alloy were developed using the aqueous solution with alkaline silicate and sodium hydroxide as a base electrolyte system.The effects of cerium（Ce） nitrate and lanthanum（La） nitrate additives on the voltage response,microstructure,compositions and corrosion resistance of PEO coatings were investigated by scanning electron microscopy（SEM）,energy-dispersive spectrum（EDS）,X-ray diffraction（XRD） and potentiodynamic polarization tests,etc.The results showed that Ce and La additives increased the stable voltage and compactness of the PEO coatings,while,those did not change the compositions of the PEO coatings.The corrosion resistance of the PEO coating obtained in solutions with La nitrate of 0.1 g/L was the best,followed by that with Ce nitrate of 0.1 g/L and that without additives.展开更多
Carbonate was added to the silicate system electrolyte to improve the corrosion resistance of the plasma electrolytic oxidation coating on Mg-9Li-3Al(wt%,LA93)alloy.The influences of carbonate on the morphology,struct...Carbonate was added to the silicate system electrolyte to improve the corrosion resistance of the plasma electrolytic oxidation coating on Mg-9Li-3Al(wt%,LA93)alloy.The influences of carbonate on the morphology,structure,and phase composition of the coating were investigated by scanning electron microscopy,energy dispersive spectrometry,X-ray diffraction,and X-ray photoelectron spectroscopy.The corrosion resistance of the coating was evaluated by electrochemical experiment,hydrogen evolution,and immersion test.The results showed that the addition of carbonate resulted in a denser coating with increased hardness,and the corrosion-resistant Li_(2)CO_(3) phase was formed.Electrochemical experiments showed that compared with the coating without carbonate,the corrosion potential of the carbonate coating positively shifted(24 mV),and the corrosion current density was reduced by approximately an order of magnitude.The coating with carbonate addition possessed a high corrosion resistance and long-term protection capability.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.
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.
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Project(1111RJDA011)supported by the Creative Research Group Fund of Gansu Province,ChinaProject(SKLAB02015006)supported by the State Key Laboratory Open Fund of Advanced Processing and Recycling of Nonferrous Metals,China。
文摘Based on orthogonal experiments,the effects of voltage,frequency,duty ratio and their interactions on the thickness and corrosion resistance of coatings prepared by plasma electrolytic oxidation(PEO)on aluminum in an alkaline silicate-containing electrolyte were investigated.The thicknesses of these coatings were obtained by measuring their cross-section using Image J software.Their corrosion resistances were evaluated in HCl and NaCl media through spot test and electrochemical test.The results show that the experimental design of this study is the key to investigate the interactions among these electrical parameters.Additionally,not only each independent factor,but also their interactions exhibit a remarkable influence on the coatings.The combination of high voltage,low frequency and large duty ratio significantly increases the coating thickness and content of the corrosion resistance phase,and thus improves the corrosion resistance of the coating in HNO3 medium.Conversely,the coating possessing the densest microstructure and best corrosion resistance in NaCl medium is obtained when low voltage and high frequency match with a small duty ratio.
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.
文摘The plasma electrolytic oxidation(PEO)procedure is utilized in order to amend the surface properties of Mg and its alloys.This procedure creates a ceramic coating on the surface applying high-voltage.The presence of deep pores and porosities in the surface that affect the corrosion resistance of the coatings is one of the PEO procedure limitations.One of the useful methods to decrease porosities of coating and improve its final properties is changing electrolyte conditions based on the presence of micro-and nanoparticles.The present paper reviews the mechanisms of particle adsorption and composition in PEO thin films in addition to the effect of particle addition on the microstructure,composition and corrosion behavior of coatings that were applied on magnesium alloys.
基金The authors would like to thank ACTICOAT project in frame of Era.NET-Rus+Call,2017(Project N477)RFBR(Project No.18-53-76008)in the frame of project ACTICOAT(Era.Net RUS Plus Call 2017,Project 477)for the partial financial support of this work.MS,MZ and CB additionally appreciate European project FUNCOAT("Development and design of novel multiFUNctional PEO COATings"in frame of H2020-MSCA-RISE-2018 call,Grant Agreement No 823942)for the financial assistance.
文摘The growth kinetics of PEO coatings on AZ31 and AZ91 magnesium alloys were studied and correlated with their structure,compositions(phase and elemental)and corrosion resistance.It was established that the coatings have a two-(outer and anodic)or three-layer structure(outer,inner and anodic)depending on the treatment time.Briefly,at short treatment time only an anodic layer and outer layer exists.Growth of the outer PEO layer takes place due to the micro discharges,which occur in vertical pores and voids with spherical cross-section.If the time is increasing,and electrolyte inside of the pores is heating-up,etching of the Mg substrate and oxide film becomes more dominant and horizontal pores in the interface between coating and metal are formed.In the pores new anodic layer will form and at this time the formation of the third inner layer starts.The growth of the inner layer happens via the anodic film as a result of micro discharge ignition in the horizontal pores,accompanied by formation of plasma in numerous micro-voids of this layer.The coatings formed on AZ91 alloy are denser,than those on AZ31,which is related to the difference in the rates of inner layer growth and dissolving of oxides which are located at the bottom of the horizontal pores.Because of the lower Al content,the AZ31 substrate itself and the also the oxide films are less stable and tend to dissolve at a higher rate compared to AZ91.Thus,it was demonstrated that a good corrosion resistance of the coatings was only obtained on AZ91 and if the average thickness of the coating is around 50μm,correlating with the formation of a sufficiently dense inner laye-Knowing this mechanism,a new two-step treatment was suggested,combining the standard PEO treatment with a subsequent PEO process in an electrolyte supporting the inner film formation.The concept was successfully applied and a further improved corrosion resistance was obtained compared to the single stage PEO process.This improvement of corrosion resistance was related to the better sealing of porosity and formation of a denser inner layer.
基金the National Natural Science Foundation of China(No.51671084)。
文摘In order to improve the wear and corrosion resistance of AZ31 magnesium alloy,a magnetron-sputtered Al layer with a thickness of 11μm was firstly applied on the alloy,and then treated by plasma electrolytic oxidation(PEO)in an aluminate and silicate electrolytes,respectively.The performance of PEO coatings was investigated by dry sliding wear and electrochemical corrosion tests.The aluminate coating exhibits excellent wear resistance under both 10 and 20 N loads.The silicate coating only shows low wear rate under 10 N,but it was destroyed under 20 N.Corrosion tests show that the Al layer after magnetron sputtering treatment alone cannot afford good protection to the Mg substrate.However,the duplex layer of PEO/Al can significantly improve the corrosion resistance of AZ31 alloy.Electrochemical tests show that the aluminate and silicate coatings have corrosion current densities of-1.6×10^(-6) and-1.1×10^(-6) A/cm^(2),respectively,which are two orders lower than that of the un-coated AZ31 alloy.However,immersion tests and electrochemical impedance spectroscopy(EIS)show that the aluminate coating exhibits better long-term corrosion protection than silicate coating.
文摘As an efficient surface modification approach,the plasma electrolytic oxidation(PEO)technique can boost the capability of wear protection in Mg and its alloys by applying a hard and thick ceramic coating.In this procedure,more efficient protection can be acquired via adding additives(in the form of particle,powder,sheet,etc.)into solutions and producing composite coatings.These additives result in more efficient protection against wear via getting stuck in the cracks and pores of coatings and rising the thickness,hardness,and diminishing the porosity size and content.The efficiency of each additive can be changed owing to its intrinsic properties like melting point,size,participation type(reactive,partly reactive,or inert)and potential of zeta.In this review,the effects of distinct additives in nano-and micro-scale size on wear behavior of PEO coatings on Mg and its alloys is going to be reviewed.
文摘In order to improve the osseointegration and antibacterial activity of titanium alloys,micro/nano-structured ceramic coatings doped with antibacterial element F were prepared by plasma electrolytic oxidation(PEO)process on Ti6Al4V alloy in NaF electrolyte.The influence of NaF concentration(0.15-0.50 mol/L)on the PEO process,microstructure,phase composition,corrosion resistance and thickness of the coatings was investigated using scanning/transmission electron microscopy,energy dispersive spectroscopy,atomic force microscopy,X-ray diffractometer,and potentiodynamic polarization.The results demonstrated that Ti6Al4V alloy had low PEO voltage(less than 200 V)in NaF electrolyte,which decreased further as the NaF concentration increased.A micro/nano-structured coating with 10-15μm pits and 200-800 nm pores was formed in NaF electrolyte;the morphology was different from the typical pancake structure obtained with other electrolytes.The coating formed in NaF electrolyte had low surface roughness and was thin(<4μm).The NaF concentration had a small effect on the phase transition from metastable anatase phase to stable rutile phase,but greatly affected the corrosion resistance.In general,as the NaF concentration increased,the surface roughness,phase(anatase and rutile)contents,corrosion resistance,and thickness of the coating first increased and then decreased,reaching the maximum values at 0.25 mol/L NaF.
文摘Magnesium has been known as an appropriate biological material on account of its good biocompatibility and biodegradability properties in addition to advantageous mechanical properties.Mg and its alloys are of poor corrosion resistance.Its high corrosion rate leads to its quick decomposition in the corrosive ambiance and as a result weakening its mechanical properties and before it is repaired,it will vanish.The corrosion and degradation rate must be controlled in the body to advance the usage of Mg and its alloys as implants.Different techniques have been utilized to boost biological properties.Plasma electrolytic oxidation(PEO)can provide porous and biocompatible coatings for implants among various techniques.Biodegradable implants are generally supposed to show enough corrosion resistance and mechanical integrity in the body environment.Much research has been carried out in order to produce PEO coatings containing calcium phosphate compounds.Calcium phosphates are really similar to bone mineral composition and present great biocompatibility.The present study deals with the usage of calcium phosphates as biocompatible coatings applied on Mg and its alloys to study the properties and control the corrosion rate.
基金supported by National Natural Science Foundation of China(51171167)Hebei Province Natural Science Foundation(A2011203068)
文摘Plasma electrolytic oxidation（PEO） coatings on AZ31 magnesium（Mg） alloy were developed using the aqueous solution with alkaline silicate and sodium hydroxide as a base electrolyte system.The effects of cerium（Ce） nitrate and lanthanum（La） nitrate additives on the voltage response,microstructure,compositions and corrosion resistance of PEO coatings were investigated by scanning electron microscopy（SEM）,energy-dispersive spectrum（EDS）,X-ray diffraction（XRD） and potentiodynamic polarization tests,etc.The results showed that Ce and La additives increased the stable voltage and compactness of the PEO coatings,while,those did not change the compositions of the PEO coatings.The corrosion resistance of the PEO coating obtained in solutions with La nitrate of 0.1 g/L was the best,followed by that with Ce nitrate of 0.1 g/L and that without additives.
基金the Natural Science Foundation of China (Nos.51771060,51871068,51971071,and 52011530025)the Domain Foundation of Equipment Advance Research of 13th Five-year Plan,China(No.61409220118)+1 种基金the Zhejiang Province Key Research and Development Program,China (No.2021C01086)the Open Foundation of Key Laboratory of Superlight Materials&Surface Technology of Ministry of Education,China (No.HEU10202104)
文摘Carbonate was added to the silicate system electrolyte to improve the corrosion resistance of the plasma electrolytic oxidation coating on Mg-9Li-3Al(wt%,LA93)alloy.The influences of carbonate on the morphology,structure,and phase composition of the coating were investigated by scanning electron microscopy,energy dispersive spectrometry,X-ray diffraction,and X-ray photoelectron spectroscopy.The corrosion resistance of the coating was evaluated by electrochemical experiment,hydrogen evolution,and immersion test.The results showed that the addition of carbonate resulted in a denser coating with increased hardness,and the corrosion-resistant Li_(2)CO_(3) phase was formed.Electrochemical experiments showed that compared with the coating without carbonate,the corrosion potential of the carbonate coating positively shifted(24 mV),and the corrosion current density was reduced by approximately an order of magnitude.The coating with carbonate addition possessed a high corrosion resistance and long-term protection capability.
