Influence of Electrolyte Concentration Variation on Thin Oxide Coating Production in Aluminum Alloy by PEO

Aluminum alloy 2024-T3 underwent Plasma Electrolytic Oxidation (PEO) treatment with sodium tetraborate solution at various concentrations. Coatings were characterized using SEM, EDS, XRD, and FT-IR. Increasing medium conductivity reduced power consumption. Alumina coatings exhibited dielectric properties, with reduced current and surface brightness during the process. Surface morphology displayed PEO characteristics, including micro-pores, remnants of discharge channels, spherical protrusions, and cracks. The coating thickness averaged 1.7 µm. XRD analysis showed a decrease in intermetallic phases and an increase in γ-Al₂O₃. Chemical analysis revealed a hybrid composition from substrate, electrolyte, and environment, including CO₂ due to Na⁺ ions' affinity for adsorbing bidentate carbonate ions.