Effect of Alkali Etching Process on Properties of Room Temperature Hard Anodized Film of Aluminum Alloy

Abstract

In order to improve the performance of aluminum alloy and optimize the anodizing process， with using sulfuric acid as the electrolyte，the normal temperature hard anodizing method was used to prepare an oxide film on the surface of 6063 aluminum alloy.Subsequently，the film performance and the effect of the alkali etching process on the film performance were studied by scanning electron microscopy， EDS testing， electrochemical testing， salt spray testing， hardness testing， and roughness testing.Results showed that under the conditions of oxidation temperature of 10 °C and oxidation time of 3 000 s， the as-obtained hard anodized film had an uneven and rough porous structure， and its corrosion resistance and physical properties were greatly improved compared to the 6063 aluminum alloy substrate.The self-corrosion potential of the hard anodized film after alkali etching treatment was－0.826 V，and the self-corrosion current was 3.892×10－6 A.No corrosion points appeared in the salt spray test for 360 h， and the corrosion resistance was good.Meanwhile， the film possessed the Vickers hardness reaches of 446 HV，the roughness Ra of 0.380 μm，the thickness of 18.86 μm，and the excellent adhesion performance.Compared with the film obtained without alkali etching， the film after alkali etching had the better corrosion resistance and physical properties such as hardness and surface roughness.

Keywords

• alkalietching|room temperature hard anodizing|sulfuric acid method|corrosion resistance