In this study, lemon juice at different concentrations as a new additive was poured into the bath of the anodizing process to enhance the mechanical properties of the manufactured aluminum oxide layers. X-ray diffraction (XRD) and field-emission scanning electron microscopy were utilized to detect formed phases and microstructure, respectively. To investigate mechanical properties, microhardness, indentation toughness, and wear tests of various aluminum oxide layers were performed. The XRD patterns showed a crystalline phase of γγ-Al2O3 for all oxide layers. The microhardness of modified layers increased up to 62.2% compared to the unmodified layer. However, by increasing the additive concentration to 2.5 vol%, the hardness decreased. This was based on increasing the pore size of layers. The lowest friction coefficient with a value of 0.53, the lowest wear rate, and the highest indentation toughness was also related to the modified aluminum oxide layer when the concentration of the additive in the bath was 0.3 vol%. For this modified layer, the value of COF/HH was the lowest, and the pore size of 50 nm was the lowest among the layers.
