An LY12 aluminum alloy was coated with a self-assembled dodecyl phosphate film by employing a novel surface-modification protocol based on the chemisorption of sodium monododecyl phosphate from aqueous solution. The effect of solution pH on the self-assembled film properties was documented, and the corrosion resistances of the self-assembled film in a Cl⁻-containing solution and in a marine atmosphere were evaluated by electrochemical impedance spectroscopy and corrosion morphology analysis. Unlike self-assembled film formed in acidic and alkaline conditions, dodecyl phosphate films formed in neutral solution exhibited a multilayer structure with greater thickness and superior corrosion resistance due to the strong chemisorption and electrostatic attraction that are fostered in neutral solutions.

The corrosion and passivation behavior of the as-cast CoCrFeNiMo_x (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) high entropy alloys (HEAs) are investigated. With the addition of Mo, increasing Mo and Cr riched σ phase precipitates from the primary FCC phase. The corrosion resistance of the CoCrFeNiMo_x HEAs strongly depends on the phase structure and the passive film. Generally, Mo promotes the selective dissolution of the FCC phase and the enrichment of Cr₂O₃ in the passive film, the former deteriorates the corrosion resistance while the latter enhances it. Interestingly, the hypoeutectic Mo_0.6 exhibits a higher corrosion resistance than that of Mo_0.4, eutectic Mo_0.8, and hypereutectic Mo₁. Analysis of surface passive film and the composition of alloy phases implies that the Cr₂O₃ enrichment dominates in Mo_0.6 while selective dissolution governs in Mo_x (x = 0.4, 0.8, and 1.0). Mo content-depended competition between the Cr₂O₃ enrichment and selective dissolution is discussed.