Effect of Anodization Treatment on the Thickness, Hardness, and Microstructural Characterization of Anodic Aluminum Oxide Film on AA 6061 and Critical Patent Analysis

Abstract

The influences of different pre-treatment approaches, comprising sandblasting, grinding, chemical polishing, and plowing, and various anodizing parameters, including electrolyte composition, temperature, current density, time, and final voltage, on the quality of anodized aluminum oxide (AAO) film on AA 6061 were studied in the present research. It was found that, during both mild and hard anodization treatment, the thickness and microhardness of AAO film increased as the anodization current density increased. Under mild anodization treatment, when the current density increased from 0.5 to 2.0 A/dm(2), the anodization efficiency decreased from 90 to 52% and 71 to 44% during the mild anodization treatment performed at 22 degrees C and 0 degrees C, respectively. However, on the other hand, the anodization efficiency increased from 55 to 56% and 57 to 64% when the current density increased from 7.0 to 8.0 A/dm(2) during the hard anodization treatment carried out at 22 degrees C and 0 degrees C, respectively. Therefore, different AAO film formation mechanisms prevail during the mild and hard anodization treatment. Moreover, the microhardness of AAO film formed at 22 degrees C or 0 degrees C dropped heavily when the current density was higher than 9.0 A/dm(2) due to the burning reaction. In addition, the AAO film can achieve higher hardness and resistance to corrosion through the sealing process, which can effectively decrease the size of the tubes due to the volume expansion effect (23%) after the sealing treatment.