Silicate and Hydroxide Concentration Influencing the Properties of Composite Al2O3-TiO2 PEO Coatings on AA7075 Alloy

This work evaluates the effect of sodium meta-silicate pentahydrate (SMS) and potassium hydroxide concentrations on properties Al2O3-TiO2 coatings produced through plasma electrolytic oxidation in a solution containing 3 g L?1 titanyl oxalate, (PTO), using unipolar waveform with constant current density. The surface cross-section characteristics PEO including morphology, elemental distribution, phase composition were evaluated FESEM, EDS, XRD techniques. Voltage-time response indicated concentration SMS KOH had significant duration each stage process. More cracks pores formed at higher concentrated solutions that resulted incorporation components especially Si into coating inner parts. Ti is distributed throughout coatings, but it dominant distribution Si-rich areas. prepared electrolyte no silicate consisted non-stoichiometric ?-Al2O3 and/or amorphous Al2O3 phase. Adding appearance ?-Al2O3 besides ?-Al2O3. corrosion behaviour was investigated EIS technique. It found presence 2 KOH, possessed highest barrier resistance (~10 M? cm2), owing to more compact outer layer, thicker layer along appropriate dielectric property because this lacks element. discovered Ti4+ Si4+ makes loss coating.