Properties and Structure of PEO Treated Aluminum Alloy

Abstract

Plasma electrolytic oxidation (PEO) coatings were formed on 7075 aluminum alloy in silicateborate based electrolyte with different duty cycles. The physical and chemical properties of the PEO coatings were thoroughly investigated. The wearing and corrosion properties of the coatings were evaluated by wearing experiments and potentiodynamic polarization tests, respectively. The results showed that the micro-hardness of the coatings first increased and then decreased with the increasing duty cycle. As a results, the wearing resistance of the coatings first increased and then decreased with the increasing duty cycle. Composition analysis proved that the coatings were mainly composed of α-Al₂O₃ and γ-Al₂O₃. The presence of wear scars on the worn surface morphology demonstrates that the three-body rolling was the main wear mechanism for coated specimen. The corrosion study showed that the coating formed in the mixed electrolyte with duty cycle of 80% showed the most superior corrosion resistance.

Keywords

7075 aluminum alloy / plasma electrolytic oxidation (PEO) / wearing / corrosion / friction coefficient