| Magnesium-lithium alloys are widely used due to their excellent properties and extraordinary development potential in the research and production of computer,aerospace,and transportation components.However,magnesium is an active metal,adding the more active metallic lithium into it makes it more susceptible to corrosion,which leads to the application of magnesium-lithium alloys is limited largely.Among various protection methods to slow down the corrosion behavior of alloys,the method of making the surface with a polymer coating is the most simple,practical and effective way,which can significantly improve the corrosion resistance of the alloys.Polymer coating is a kind of coating with stable performance and strong protection to alloys.In this paper,polyaniline(PANI)and epoxy resin are combined to prepare a PANI/epoxy composite coating.Since the bonding force between the PANI/epoxy resin composite coating and the substrate is not ideal,the silane coupling agent can be a link between the polymer coating and the substrate and enhancing the bonding force of them greatly.Corrosion inhibitors can also alleviate the corrosion rate of magnesium-lithium alloys.Therefore,this article studied the influence of corrosion inhibitors on the corrosion behavior of magnesium-lithium alloys firstly,and then prepared silane conversion coatings on magnesium-lithium alloy substrates,and prepared polymerization based on them finally.A series of tests were characterized the corrosion resistance of the coating.The electrochemical corrosion behavior of magnesium-lithium alloy was studied.Sodium polyphosphate and nicotinamide were added as corrosion inhibitors to 3.5 wt% Na Cl solution to perform corrosion treatment on magnesium-lithium alloy.The influence of corrosion inhibitors on the corrosion behavior of magnesium-lithium alloys was characterized by metallographic microscope(OM),X ray diffractometer(XRD),scanning electron microscope(SEM)and other instruments.Using single factor experiments to explore the effects of silane concentration,alcoholysis time,p H value,curing temperature and curing time of two different kinds of silane coupling agents,bis(1,2-triethoxysilyl)ethane(BTSE)and bis(?-triethoxysilylpropyl)tetrasulfide(Si69).And mixed the corrosion inhibitor with the silane solution.Corrosion resistance of the silane film was characterized by the polarization curve(Tafel)and impedance(EIS)and other electrochemical tests,surface morphology,X ray photoelectron spectroscopy(XPS)and Fourier Transform infrared spectroscopy(FTIR).Choosing a group of the better experimental conditions of the two coupling agents respectively,and then used in combination.The better experimental conditions were finally determined by comparative analysis,alcohol-water volume ratio 5:1,alcoholysis time 24 h,Si69 silane solution concentration 10%,p H value 5,BTSE silane solution concentration 4%,p H value 6,volume ratio Si69:BTSE=3:1,curing time10 min,curing temperature 100 ?.Silane films with corrosion inhibitors showed better corrosion resistance.A polymer coating was applied to the surface of the magnesium-lithium alloy after the corrosion inhibitor silane film treatment,and the effect of different proportions of polyaniline/epoxy resin composite and curing time on the coating performance were explored.The PANI/epoxy resin coating was coated on the surface of the magnesium-lithium alloy by dipping.Electrochemical tests such as polarization curve and impedance spectroscopy,bonding performance test and salt spray test were used to characterize the corrosion resistance of polymer coatings.The final optimal experimental conditions were PANI concentration 15%,curing time 24 h.The corrosion resistance of the PANI/epoxy resin composite coating to the magnesium-lithium alloy had been significantly improved. |
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