Incorporation mechanism of colloidal TiO2 nanoparticles and their effect on properties of coatings grown on 7075 Al alloy from silicate-based solution using plasma electrolytic oxidation

Plasma electrolytic oxidation (PEO) was applied using a pulsed unipolar waveformto produce Al2O3−TiO2 composite coatings from sol solutions containing colloidal TiO2 nanoparticles. The were produced by dissolving 1, 3, and 5 g/L of potassium titanyl oxalate (PTO) in silicate solution. Scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, Raman spectroscopy to characterizing the coatings. Corrosion behavior investigated polarization impedance techniques. results indicated that enters coating through all types micro-discharging is doped into alumina phase. higher level incorporation decrease surface micro-pores, while lower shows reverse effect. It revealed content makes more compact outer layer increases inner thickness coating. Electrochemical measurements obtained solution 3 PTO exhibits corrosion performance than absence PTO. consists γ-Al2O3, δ-Al2O3 amorphous phases, α-Al2O3 promoted presence