Research On The Preparation Process And Properties Of Hard Anodizing On Aluminium Alloy Surface

Aluminum and its alloys are widely used in production and life due to their advantages of low relative density,high specific strength and easy forming.As a surface treatment technology with simple operation and low cost,anodic oxidation technology has a good application prospect in aerospace,rail cars,shipbuilding and other fields.In recent years,with the continuous expansion of its application,the traditional anodic oxidation technology can not meet the rapid growth of modern industry demand.Therefore,it is necessary to improve and innovate the anodic oxidation process and optimize the process parameters to prolong the service life of aluminum alloy materials.In this paper,hard anodic oxide film of 7075 aluminum alloy was prepared in the mixed acid electrolyte of sulfuric acid and boric acid.The effects of oxidation temperature,current density and oxidation time on the thickness,hardness,microstructure and surface roughness of hard anodic oxidation film of 7075 aluminum alloy were studied.The wear properties of hard oxide film under different technological parameters were analyzed by using Micro-nano-mechanical comprehensive testing system.Electrochemical workstation and salt spray corrosion test chamber were used to test and analyze the corrosion resistance of hard oxide film.The results show that the current density and oxidation time have the greatest influence on the oxide film thickness.When the current density is high,the film formed by oxidation is thicker.In a certain time range,the longer the oxidation time,the thicker the oxide film.The maximum thickness of oxide film prepared in this experiment is up to127.40?m.The main factors affecting the hardness of oxide film are oxidation temperature and current density.With the increase of temperature and current density,the hardness of the film increases first and then decreases.Under the experimental conditions,the hardness of hard anodic oxide film is up to 417 HV.Through the study of hard anodizing of 7075 aluminum alloy,it can be concluded that the current density has the greatest influence on the wear property of oxide film,followed by the oxidation temperature.The friction coefficient of oxide film obtained under low temperature and low current density process is generally small,and the wear resistance is excellent.After hard anodizing treatment,the corrosion resistance of the sample will be greatly improved.Through electrochemical analysis,the current density is the most important factor affecting the corrosion resistance of the oxide film.With the increase of current density,the corrosion resistance of oxide film increases first and then decreases.When the current density is 3 A/dm²,the corrosion resistance of the oxide film is the best.Comprehensive analysis of performance in all aspects,it is concluded that the optimal process parameters for the preparation of 7075 aluminum alloy hard anodic oxide film under the experimental conditions are:T=-1?,J=3 A/dm²,t=60 min,c(H₂SO₄)=180 g/L,c(H₃BO₃)=10 g/L.The hard oxide film prepared by this process is black in color,with uniform surface and metallic luster.The thickness of the film is 69.31?m,the micro-hardness is 417 HV,and the wear resistance is excellent.