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
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.
