Protective properties of the nanocomposite coatings on Mg alloy

摘要

Nanocomposite coatings were obtained by aggregation of nanoparticles from dispersion in decane on the surface of oxide coatings. Oxide coatings on magnesium alloy were formed by plasma electrolytic oxidation in silicate containing electrolyte in bipolar mode. Electrochemical properties and stability of nanocomposite coatings under conditions of prolonged exposure to chloride containing environment were studied by means of electrochemical impedance spectroscopy, potentiodynamic polarization and measurements of contact angles. The coatings possess superhydrophobic properties with the contact angle of 166° ± 3° and the rolling angle of 5° ± 3°. It was found that these nanocomposite coatings reduce the corrosion current of magnesium alloy by more than three orders of magnitude. High stability during immersion in aggressive media is due to a small contact area of the coatings with electrolyte and high adhesion of the hydrophobic agent molecules with the coating.