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
Plasma electrolytic oxidation(PEO)coatings developed under voltage-controlled mode on various commercial wrought,gravity cast and rheocast aluminium alloys were discussed with respect to enhancement of their tribologi...Plasma electrolytic oxidation(PEO)coatings developed under voltage-controlled mode on various commercial wrought,gravity cast and rheocast aluminium alloys were discussed with respect to enhancement of their tribological and corrosionperformance and minimization of the PEO energy consumption.It is demonstrated that use of conventional porous anodic filmprecursors reduces the PEO energy consumption by up to50%.The wear of6082alloy with PEO coatings with addedα-Al2O3particles is two times lower compared with electrolytic hard chrome.The long-term corrosion resistance of the PEO-coatedA356rheocast alloy is enhanced via use of a precursor and hydrophobic post-treatment.展开更多
Zinc aluminium(Zn-Al)and lithium aluminium(Li-Al)–layered double hydroxides(LDH)coatings with incorporated inhibitors(Li-,Mo-and W-based)were successfully synthesized on AZ31 Mg alloy.Zn-Al LDH W and Li-Al LDH Li sho...Zinc aluminium(Zn-Al)and lithium aluminium(Li-Al)–layered double hydroxides(LDH)coatings with incorporated inhibitors(Li-,Mo-and W-based)were successfully synthesized on AZ31 Mg alloy.Zn-Al LDH W and Li-Al LDH Li showed the highest corrosion resistance and were selected for further evaluation.SEM cross-section examination revealed a bi-layer structure composed of an outer part with loose flakes and a denser inner layer.XRD,FTIR,and XPS analysis confirmed the incorporation of the inhibitors.Post-treatments with corrosion inhibitors containing solutions resulted in the selective dissolution of the most external layer of the LDH coating,reducing the surface roughness,hydrophilicity and paint adhesion of the layers.Active corrosion properties were confirmed by SVET evaluation for the Zn-Al LDH W coating.The proposed active corrosion mechanism involves the ion-exchange of aggressive Cl-ions,deposition of hydroxides and competitive adsorption of W-rich corrosion inhibitors.展开更多
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the support of PID2021-124341OB-C22 and PID2021-124341OB-C21(MCIU/AEI/FEDER,UE)ADITIMAT-CM(S2018/NMT-4411,Regional Government of Madrid and EU Structural Funds)+2 种基金the support of RYC-2017-21843the support of PEJD-2019-POST/IND-16119(Regional Government of Madrid and EU Structural Funds)FEI-EU-20-05(UCM)。
基金supported by Regional Government of Madrid and EU Structural Funds via Multimat Challenge Programme(S2013/MIT-2862-CM)Proyecto Retos Jovenes Investigadores Programme(MAT2015-73355-JIN)funded by MINECO,Spain
文摘Plasma electrolytic oxidation(PEO)coatings developed under voltage-controlled mode on various commercial wrought,gravity cast and rheocast aluminium alloys were discussed with respect to enhancement of their tribological and corrosionperformance and minimization of the PEO energy consumption.It is demonstrated that use of conventional porous anodic filmprecursors reduces the PEO energy consumption by up to50%.The wear of6082alloy with PEO coatings with addedα-Al2O3particles is two times lower compared with electrolytic hard chrome.The long-term corrosion resistance of the PEO-coatedA356rheocast alloy is enhanced via use of a precursor and hydrophobic post-treatment.
基金the support of the RTI2018-096391-B-C33 FEDER/Ministerio de Ciencia e Innovación-Agencia Estatal de InvestigaciónS2018/NMT-4411 Regional Government of Madrid+2 种基金EU Structural and Social Funds and PID2021-124341OBC22(MCIU/AEI/FEDER,UE)the support of RYC-201721843,Ministerio de Ciencia e Innovaciónsupported by the Royal Academy of Engineering through the RAEng Research Fellowship and by EPSRC(EP/V026097/1)。
文摘Zinc aluminium(Zn-Al)and lithium aluminium(Li-Al)–layered double hydroxides(LDH)coatings with incorporated inhibitors(Li-,Mo-and W-based)were successfully synthesized on AZ31 Mg alloy.Zn-Al LDH W and Li-Al LDH Li showed the highest corrosion resistance and were selected for further evaluation.SEM cross-section examination revealed a bi-layer structure composed of an outer part with loose flakes and a denser inner layer.XRD,FTIR,and XPS analysis confirmed the incorporation of the inhibitors.Post-treatments with corrosion inhibitors containing solutions resulted in the selective dissolution of the most external layer of the LDH coating,reducing the surface roughness,hydrophilicity and paint adhesion of the layers.Active corrosion properties were confirmed by SVET evaluation for the Zn-Al LDH W coating.The proposed active corrosion mechanism involves the ion-exchange of aggressive Cl-ions,deposition of hydroxides and competitive adsorption of W-rich corrosion inhibitors.
