Aluminum, a sought-after non-ferrous metal in manufacturing, boasts numerous advantages, such as being lightweight, having good corrosion resistance, and having excellent electrical conductivity. However, it faces drawbacks like low hardness, poor abrasion resistance, and susceptibility to deformation. Anodizing is a viable solution to enhance aluminum’s properties, including hardness, abrasion resistance, and visual appeal. This study investigates the impact of varying electrolyte solution concentrations on mass changes, microstructure alterations, coating thickness, and aluminum hardness. Employing a consistent voltage of 20 V and a current of 6 A for 30 min, the experiment tests electrolyte solution concentrations of 5%, 10%, 12%, and 15% sulfuric acid (H₂SO₄). Results indicate that the highest hardness values, averaging 74.87 Vickers Hardness Number (VHN), occur at the 15% concentration, whereas the lowest, averaging 67.23 VHN, appear at the 5% concentration. Coating thickness measurements reveal that the thickest layers, averaging 21.08 μm on the front and 6.61 μm on the back, are achieved with the 15% concentration. In contrast, the thinnest layers, averaging 6.84 μm on the front and 5.17 μm on the back, are observed at the 5% concentration. Microstructural analysis shows the most significant presence of pits at the 15% concentration and the least at the 5% concentration. Mass change tests highlight a 0.7 g difference and a 4.09% increase in mass at the 15% concentration, compared to a 0.4 g difference and a 2.29% increase at the 5% concentration. Higher electrolyte solution concentrations correspond to increased hardness values, impacting mass, microstructure, and oxide layer thickness.