High performance alumina films prepared by direct current plus pulse anodisation

Abstract

Traditional anodic aluminium oxide (AAO) is usually fabricated by potentiostatic method at 0–5°C to inhibit the joule’s heat enhanced dissolution in aluminium oxide for well ordered cell configuration. In this paper, AAO film was performed by direct current plus pulse (DCP) method in mixed acid (sulphuric acid–tartaric acid–oxalic acid) and Al₂(SO₄)₃ electrolyte at room temperature. Effects of anodising voltages on anticorrosion, nanohardness and elastic modulus of 2024 aluminium alloy oxide films were investigated by electrochemical polarisation and nanoindentation. By means of DCP technique, the alumina films were fabricated by anodising 2024 Al under high potentials (E2) from 18 to 23 V and low potentials (E2) from 16 to 21 V. It was found that the anodised films fabricated under the voltage of 21–19 V could exhibit excellent performance. Meanwhile, the results showed that anticorrosion, nanohardness and Young’s modulus were significantly affected by anodising voltages, which were attributed to the changes of anodised film density as well as the pore wall thickness according to the SEM analysis.

Keywords:

• Aluminium
• Anodic oxide film
• Direct current plus pulse
• Anticorrosion