Formation of multi-functional TiO2 surfaces on AA2024 alloy using plasma electrolytic oxidation

Lj. Damjanović-Vasilić,P. Karlova,S. Karpushenkov,M. Serdechnova,S. Stojanović,D.C.F. Wieland,C. Blawert,S. Ignjatović,M.L. Zheludkevich,M. Starykevich,M. Damjanović

doi:10.1016/j.apsusc.2020.148875

Lj. Damjanović-Vasilić, P. Karlova + Show 9 more

Open Access

https://doi.org/10.1016/j.apsusc.2020.148875

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Abstract

Plasma electrolytic oxidation (PEO) was applied to functionalise the surface of AA2024 alloy. A potassium titanium-oxide oxalate dihydrate based aqueous electrolyte was used, which allowed the direct formation of a TiO2 surface layer on the aluminium alloy substrate. The effect of PEO treatment time and the additional presence of anatase particles in the electrolyte solution on the surface layer and its properties (corrosion, wear and photocatalytic activity) were investigated.It was found that the coating thickness and surface morphology are strongly dependent on the PEO processing time. However, the phase composition is not much affected by the treatment time and the main coating phase is rutile with a smaller amount of anatase. Adding additional anatase in the form of particles increases the amount of anatase in the coatings. The additional particle addition has only minor effect on the corrosion resistance, but reduces the wear resistance remarkably. Interestingly, the addition of anatase particles and the PEO treatment time are not effective in increasing the photocatalytic activities of the samples.

Highlights

Plasma electrolytic oxidation, known as micro arc oxidation or anodic spark deposition is a surface engineering technology, which is considered to be one of the most cost-effective and environmentally friendly ways to produce stable oxide coatings on the surface of light weight metals and their alloys.The main constituents of the PEO coating are high-temperature oxide phases, which are synthesized inside the dielectric discharge channels out of substrate and electrolyte species
The size of micro-discharges becomes larger with increasing time of PEO processing, while their population decreases
The number of pores and their density decreases with increasing PEO processing time, but the pores grow in size

Summary

Introduction

The main constituents of the PEO coating are high-temperature oxide phases, which are synthesized inside the dielectric discharge channels out of substrate and electrolyte species This is possible due to high local temperatures and instantaneous plasma formation, which lead to rapid heating and cooling of the oxide layer [1,2,3,4,5,6,7,8]. Such coatings consist of substrate metal oxides, and products of physicochemical transformations of electrolyte components under the effect of electrical discharges. With the additional influence of electrolyte and substrate a large variety of

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