This study 7075 aluminum alloy was used as the substrate. Ceramic coatings are fabricated via micro-arc oxidation (MAO) under regulated frequencies of 100, 400, 700 and 1000 Hz, followed by hydrophobic modification with stearic acid. The effects and mechanisms of frequency on microstructure, surface wettability and corrosion resistance of coatings are systematically investigated. The results reveal that MAO frequency greatly alters the micromorphology and porosity of coatings. The coating prepared at 400 Hz possesses the densest structure with the minimum porosity of approximately 1.24%. By contrast, the porosity rises to around 2.13% and 3.95% at 100 Hz and 1000 Hz respectively. After stearic acid modification, the surface contact angle increases remarkably from 43.2°—59.1° to 117.8°—123.4°, endowing the coatings with low surface energy. The modified coating obtained at 400 Hz achieves the maximum contact angle of 123.4° and the lowest surface energy of 15.45 mJ/m2. Electrochemical tests demonstrate that the MAO coating formed at 400 Hz exhibits the lowest corrosion current density of (1.05×10-9 A/cm2) and the highest polarization resistance of (4.91×107 Ω·cm2). Excellent corrosion resistance is maintained after hydrophobic modification, with the polarization resistance reaching about (1.45×107 Ω·cm2). Neutral salt spray tests show that no obvious corrosion occurs on modified coatings after 504 hours, while corrosion products accumulate on unmodified specimens. It is confirmed that MAO frequency adjusts discharge behavior to tailor pore structure and surface state, thereby determining hydrophobic modification efficiency and corrosion protection capacity. The coating prepared at 400 Hz delivers optimal comprehensive properties. This work provides a theoretical reference for the design and fabrication of high-performance protective coatings on aluminum alloy surfaces.