Preparation And Performance Study Of Conversion Coating Of AZ91D Magnesium Alloy

Magnesium as earth resource is rich in mineral resources,the people take care of them now.Magnesium alloy has the small density,the high specific strength,the big specific modulus,good heat dissipation,good shock resistance,bear impact load ability than aluminum alloy,good corrosion resistance of organic matter and alkali.Magnesium alloy meets the aerospace,medical equipment,electronic products and so on because of it's advantages,but because of the magnesium alloy corrosion resistant performance is poor,making magnesium alloys is limited in applications,impacting the development.Therefore,the corrosion resistance of magnesium alloys research is the key of the surface treatment.In order to solve the problem of magnesium alloy poor corrosion resistant,nowadays there are many methods of surface treatment.Based on the simple,rapid,efficient,green environmental protection as the foundation,by chemical means,form a layer with corrosion resistant performance on the surface of AZ91D magnesium alloy.This article has two systems:phytic acid and zirconate,respectively,the two systems conversion coating on AZ91D magnesium alloy surface.Though single factor experiment,optimize the experimental conditions,eventually relatively better film forming conditions were determined.By neutral salt spray test,electrochemical testing research corrosion resistant properties of film.By scanning electron microscope?SEM?and EDS research microstructure and elements of the film.Through these characterization methods,the corrosion resistance of magnesium alloys,microstructure,element composition were characterized.Studies have shown that the best composition and process conditions of phytic acid system are:C₆H₁₈O₂₄P₆ 0.5-1.0g/L,NaVO₃ 1g/L,Ni?NO3_?3 1g/L,LaCO₃ and Ce?CO₃?₂ 0.3g/L.Film-forming temperature is 70?,film forming time is 30 min.The neutral salt spray test time can be up to 24 h.The best composition and processconditions of zirconate system are: K₂ZrF₆ 5g/L,NaVO₃ 1g/L,C₇₆H₅₂O₄₆ 0.5g/L,Na₂MoO₄ 0.3g/L.Film-forming temperature is 70?,film forming time is 50 min.The neutral salt spray test time can be up to 20 h.In this paper,we study the two kinds of transformation fluid,form the film on the magnesium alloy,these corrosion resistant performance are pretty good.Due to its less dose,simple operation,good membrane layer,make it have pretty applicable value.