Monododecyl Phosphate Film on LY12 Aluminum Alloy: pH-Controlled Self-Assembly and Corrosion Resistance

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.