Thermal conductivity of PEO-coated AlMg3 samples with different particle additions

Efficient thermal management is essential for aluminum components operating in environments with fluctuating thermal loads, especially when protective surface treatments are required, like in heat exchangers working in phase change material (PCM) environments. Plasma electrolytic oxidation (PEO) provides excellent wear and corrosion resistance but typically produces ceramic layers with low intrinsic thermal conductivity, potentially limiting heat-transfer performance. This study systematically evaluates how PEO processing mode (unipolar vs. bipolar) and nanoparticle additives influence coating microstructure, phase composition, porosity, and the effective thermal conductivity of coated AlMg3 substrates. Coatings were produced using a standard alkaline silicate-phosphate electrolyte with and without ZnO, WS 2 , TiC, TiN, and BN particles. Microstructural and compositional analyses were performed via SEM/EDS and GIXRD measurements, while thermal conductivity of the full coated system was determined using laser flash analysis (LFA). Across all conditions, PEO coatings reduced thermal conductivity relative to bare alloy (129.78 W/(m·K)) but only moderately, with most 5-min treatments remaining within ∼20% loss of the substrate conductivity (111.43 W/(m·K) for particle-free unipolar mode coatings). Particle additions resulted only in limited improvements; the best performing additive, 3 g/L ZnO in unipolar mode, yielded slight conductivity enhancement associated with more uniform particle incorporation (119. 03 W/(m·K)). Overall, results highlight that PEO coatings can deliver protective functionality while maintaining acceptable thermal performance.