STUDY ON PULSE ANODIZING OF 6061 ALUMINUM ALLOY AND ITS CORROSION RESISTANCE AND MECHANICAL PROPERTY

The 6061-aluminum alloy is anodized by pulse anodizing method in the solution with sulfuric acid and oxalic acid to improve its corrosion resistance and mechanical properties greatly. Different duty cycles ranging from 0.2 to 0.8 are applied during the pulse anodizing process to study the influence of duty cycles on the thickness, roughness, composition, surface morphology, corrosion, and wear resistance performance of the oxide films obtained on the surface of 6061 aluminum alloy. The anodizing process of aluminum alloy in an acid solution is accompanied by the formation and dissolution of oxide film. The duty cycle impacts the thickness and roughness of the oxide film. With the increase of the duty cycle from 0.2 to 0.6, the thickness of the oxide film is increased from 21.2 to 38.7[Formula: see text] [Formula: see text]m while the roughness of the oxide film gradually increases from 0.237 to 0.674[Formula: see text] [Formula: see text]m. However, the thickness of the oxide film is decreased obviously to 31.1[Formula: see text] [Formula: see text]m when the duty cycle applied is 0.8 due to thermal effects and stress-induced cracking. The surface of oxide films presents many pores and agglomerated alumina composed of the elements of aluminum (Al), oxygen (O), sulfur (S), and carbon (C). A higher duty cycle is beneficial to increase the growth rate and size of agglomerated alumina on the surface of the oxide film. Some micro-cracks can be observed on the surface of the oxide film anodized using a 0.8-duty cycle. After the pulse anodizing treatment, the hardness of anodized aluminum alloys improves significantly. With the increase of the duty cycle from 0.2 to 0.8, the hardness of the oxide film ranged from approximately 300–550[Formula: see text]HV. The oxide film anodized using a 0.6 duty cycle presents the best wear resistance and optimal corrosion resistance with the smallest wear rate of 1.043 × 10[Formula: see text] [Formula: see text]mm3/Nm and the smallest corrosion current density of 9.73[Formula: see text] [Formula: see text]A/cm2.