Formation And Characterization Of Red Zr-Se Conversion Coatings On Aluminum Alloy

This paper mainly studies and analyze the development process and the best process performance of a kind of environmentally friendly aluminum alloy conversion coating formula.The conversion film is mainly composed of zirconium fluoride acid potassium and selenium dioxide as the main salt,NaF as accelerator,MgSO₄ as film-forming promoter,phytic acid as the adhesion agent.This conversion film is prepared on aluminum alloy layer under the appropriate temperature conditions.The research process aluminum alloy conversion coating formula,mainly adopts the single factor experiment,through the analysis each influence of film forming factors on the electrochemical performance of the conversion coating,film-forming optimum process is determined.Through the analysis of the best formula of surface conversion coating for aluminum alloy:zirconium fluoride potassium:0.25-0.5g/L,selenium dioxide:0.5-0.75g/L,magnesium sulfate:0.75-1.00g/L,NaF:0.75-1.00g/L,phytic acid:0.75-1.00g/L,the temperature is room temperature,the processing time is 10¹5 min,pH value of 4⁶.The conversion coating layer prepared under this process condition,uniform,continuous coverage in the aluminum alloy surface with a dark red,and is conducive to industrial production.Optimum conversion coating layer,through electrochemical measurements can be found,after dealing with the transformation of aluminum alloy from corrosion current density is far less than that without the conversion process of aluminum alloy,at the same time membrane layer of the resistance of untreated increased from 63.56?to 485?,so that after dealing with the transformation of the corrosion resistance of aluminum alloy gained great improve.And after dealing with the transformation of aluminum alloy with the traditional chromate after intravenous drip experiment can be found that the corrosion resistance of both time difference is small,that after dealing with the transformation of the corrosion resistance of aluminum alloy with the traditional chromate conversion coating corrosion resistance.After dealing with the transformation of film,under SEM characterization,can find many elliptical particles evenly attached on the surface of aluminum alloy.Under the EDS and XPS characterization,to draw a conversion coating layer mainly by Na₃AlF₆,ZrO₂,Se and organic substances such as form chelate complex,and the preparation of the conversion coating layer is a highly heterogeneous complicated system.