This study investigates the influence of micro-arc oxidation (MAO) duration on the formation and characteristics of ceramic coatings on 6061 aluminum alloys. MAO treatments were conducted in a silicate-based electrolyte for varying durations. The effects of oxidation time on film thickness, surface roughness, morphology, and phase composition were meticulously assessed using a film thickness gauge, surface roughness meter, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. The corrosion behavior of the coatings was evaluated in a 3.5% NaCl solution using an electrochemical workstation. The experimental results demonstrate that both the film thickness and surface roughness exhibit a positive correlation with oxidation time. Notably, the film growth rate initially increased before plateauing, suggesting an optimal oxidation duration. The coatings primarily comprise γ-Al₂O₃, α-Al₂O₃, and Al phases, with the proportions of γ-Al₂O₃ and α-Al₂O₃ increasing progressively with extended oxidation times. Comparative electrochemical tests revealed that the treated specimens exhibited significantly higher corrosion potential and reduced corrosion current densities compared to the untreated aluminum alloy substrate. Specifically, a coating produced with a 20 min oxidation time demonstrated an exceptional corrosion current density (J_corr) of 1.545 × 10⁻⁶ A·cm⁻² and a corrosion resistance (R_p) of 2.716 × 10⁴ Ω·cm², signifying the best corrosion resistance achieved in this study. These results underscore the pivotal role of oxidation time in tailoring the properties of micro-arc-oxidized layers on 6061 aluminum alloys, offering valuable insights for enhancing corrosion protection in practical applications.

We investigate the influence of the NaOH to KF ratio in a silicate electrolyte on the corrosion resistance and tribological properties of micro-arc oxidation (MAO) coatings on a 6061 aluminum alloy. By optimizing the electrolyte composition, we achieved significant improvements in coating quality. The surface morphology and composition of the coatings were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Our findings reveal that the coatings produced at a 2:1 NaOH/KF ratio exhibited superior corrosion resistance, with a corrosion potential of −1.279 V, corrosion current density of 1.85 × 10⁻⁷ A·cm⁻², and protective resistance of 1.50 × 10⁵ Ω·cm². Additionally, the surface roughness and coating thickness were measured at 0.68 μm and 8.04 μm, respectively, providing a robust foundation for enhancing the anticorrosive and wear-resistant properties of 6061 aluminum alloy.

To elucidate the effects of TiO₂ nanoparticles on the microstructure and corrosion resistance of micro-arc oxidation (MAO) coatings formed on 6061 aluminum alloy, MAO coatings were prepared in a silicate-based electrolyte with varying TiO₂ nanoparticle concentrations. The coating structure and properties were evaluated using a coating thickness gauge, surface profilometer, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and an electrochemical workstation. The results show that, with increasing TiO₂ content, both coating thickness and surface roughness gradually increase, while the surface porosity first decreases and then increases. An appropriate amount of TiO₂ effectively lowers the surface porosity and enhances coating compactness. The T₁ condition exhibited the least precipitation of corrosion products during immersion tests and thus the best corrosion resistance. Compared to the untreated 6061 aluminum alloy substrate, the optimized coating demonstrated a reduction in corrosion current density (J_corr) by more than one order of magnitude, reaching 1.127 × 10⁻⁶ A·cm⁻², while its polarization resistance (R_p) increased by over one order of magnitude, attaining 3.558 × 10⁴ Ω·cm². Furthermore, relative to the TiO₂-free T₀ coating, the J_corr of the optimized coating was further reduced by approximately 2.5 times, with its R_p enhanced by about 2.3 times. XRD analysis indicated that the MAO coatings primarily consist of α-Al₂O₃ and γ- Al₂O₃. This study provides theoretical and experimental support for the application of TiO₂ nanoparticles in MAO processes.