Influence of duty cycle on surface characteristic and adhesion of CuO composite PEO on AA 6061 aluminum alloy

This study investigates the influence of duty cycle on the surface characteristics and adhesion strength of CuO composite plasma electrolytic oxidation (PEO) coatings on AA6061 aluminum alloy, for passive cooling applications. The coatings were fabricated using an AC bipolar pulse with anodic duty cycles of 10%, 20%, and 40% in a KOH-Na₃PO₄ electrolyte containing synthesized Cu₂O nanoparticles. Surface analysis revealed that increasing the duty cycle led to a reduction in porosity, enhanced uniformity, and a smoother morphology, which is crucial for improving the adhesion strength. The incorporation of Cu₂O NPs significantly modified the structural and mechanical properties of the coatings, imparting dark characteristics surfaces that enhance radiative heat dissipation. XRD analysis demonstrated the formation of γ-Al₂O₃ and α-Al₂O₃ phases, with higher duty cycles promoting increased α-Al₂O₃ content, known for its superior mechanical stability. Adhesive strength measurements indicated that 40% duty cycle composite PEO coating exhibited the highest adhesion strength, attributed to the prolonged anodic period. Although the coating thickness slightly decreased at higher duty cycles, the improved adhesion and microstructural integrity enhanced the durability of the coating. These findings suggest that controlling the duty cycle in CuO composite PEO processes offers a promising approach for creating high-quality protective coatings on aluminum alloys for passive cooling applications.