Microstructure and multi-scale mechanical behavior of hard anodized and plasma electrolytic oxidation (PEO) coatings on aluminum alloy 5052

► Hardness of the PEO coating was three times that of the anodized coating. ► Good agreement between Vickers, Knoop and Berkovich hardness on coating thickness ► Indentation stress-strain curves were measured across the coating thickness. ► Scratch tests suggest both coatings to be extremely well adhered to the substrate. ► Micro-scratch resistance was found to scale similarly to hardness.