Research On Organic/Inorganic Composite Coating For Integrated Anticorrosion And Wear Resistance On Magnesium Alloy Surface

As a new green engineering material,magnesium alloy has great application prospects in many equipment manufacturing fields.However,the poor corrosion resistance and wear resistance of magnesium alloys seriously limits its service life and applications.At present,surface coatings are often used to improve the surface protection capabilities of magnesium alloys.However,a single organic or inorganic coating has certain drawbacks.The mechanical properties of organic coatings are poor,while the compactness of inorganic coatings is poor.Therefore,in this paper,in order to prepare a composite coating with integrated corrosion resistance and wear resistance,two inorganic materials with layered structure were selected as the framework,and the organic material was selected as modifier.The detailed research content was as follows:1)Graphene oxide(GO)with a two-dimensional layered material was prepared by the Hummer method.Stearic acid(SA)was grafted onto the graphene oxide sheet,and SA-GO composite coating was prepared on magnesium alloy by self-assembly method.Electrochemical test results showed that SA-GO coating could significantly improve the corrosion resistance of the magnesium alloys,which was attributed to the decrease of the porosity of the graphene oxide sheet after the grafting and the increase of the hydrophobicity.In addition,compared with the magnesium alloy substrate,the wear rate of the SA-GO coating was reduced by 99.3%,which was attributed to the anti-wear effect of graphene oxide sheets and the self-lubricating property of SA.2)The in-situ growth method was used to prepare a strong bonding Layered Double Hydroxide(LDHs)coating on magnesium alloys surface.Then,to fabricate a tri-layer composite coating with strong bonding force,the silane and GO were sequentially bonded onto the surface by selfassembly method.The electrochemical results indicated that the corrosion resistance of Mg alloy was greatly improved.It was attributed to the strong binding force,the ion exchange capacity and the good barrier effect of the composite coatings.Moreover,compared with the bare magnesium alloy,the wear rate of the composite film was reduced by 94%.It was attributed to the reduction of surface roughness and the good anti-wear property of GO and LDHs.3)A super-hydrophobic composite coating based on LDHs was fabricated on the surface of Mg alloys by laser treatment,in-situ growth of LDHs,and modification with octadecyl-trimethoxy-silane(OTS).Results showed that the composite coating presented the best anti-corrosion performance and the corrosion current density was reduced by 5 orders of magnitude compared with that of the Mg alloy substrate.The corrosion resistance was attributed to the super-hydrophobicity of the composite coating,the compactness and ion exchange capacity of the LDHs layer and the dense Si-O-Si network within OTS layer.Moreover,the composite coating exhibited the excellent long-term stability,which was attributed to the existence of hydrophobicity of the composite coating and the selfhealing ability of LDHs.In addition,the composite coating also has good wear resistance,which was mainly attributed to the compactness and structure of the composite coating and the anti-wear effect of LDHs.