The work aims to study the effect of argon ion bombardment on the structure and corrosion resistance of Al film on TC4 titanium alloy, and to provide theoretical basis for the surface corrosion protection of aeronautical titanium alloy fasteners. The Al film was prepared on the surface of Ti-6Al-4V (TC4) titanium alloy substrate by magnetron sputtering ion plating combined with middle frequency and direct current. The influence of film thickness and corrosion time on the corrosion resistance was studied by electrochemical method. In addition, with the post-treatment of the film by argon ion bombardment, the influence of argon ion bombardment on the corrosion resistance of Al film was explored, the SEM, EDS and AFM were used to characterize the interfacial morphology and to analyze the corrosion mechanism. The micro hardness tester and micro-nano scratch tester were applied to test the surface hardness and adhesion strength. With the increase of film thickness from 11.1 μm to 15.9 μm, the corrosion current density decreased about 76.6%, and when the thickness increased from 15.9 μm to 20.3 μm, the corrosion current density decreased by 24.3%. As the immersion time reached 24 h, the accumulation and coverage of corrosion products in the loose oxide film hindered the corrosion of the Al film. For 48~72 h, the corrosion of the Al film was aggravated gradually with the exfoliation of the relatively loose corrosion products. The macroscopic corrosion pits appeared on the surface of the film after 96 h. After Ar+ ion bombardment, the surface roughness increased, the self-corrosion current density of aluminum film decreased from 1.65×10-8 A/cm2 to 7.29×10-8 A/cm2. With the increase of the thickness of the aluminum film, the corrosion resistance is gradually enhanced. The film has strong corrosion resistance in the early and middle stages of immersion, and the pitting corrosion occurs in the film after later immersion stage, and the corrosion resistance of the film decreases. After argon ion bombardment, the corrosion resistance, microhardness and interfacial bonding properties of the film are improved.