Protective Composite Coatings Formed on Mg Alloy Surface by PEO Using Organofluorine Materials

The results of the surface modification of magnesium alloys by plasma electrolytic oxidation (PEO) and subsequent treatment in suspension of the superdispersed polytetrafluoroethylene (SPTFE) or telomeric solution of tetrafluoroethylene (TFE) are presented. Composite coatings have been obtained by dipping with subsequent heat treatment. Electrochemical, tribological properties and wettability of protective composite coatings have been investigated. Composite coatings formed on PEO-layer by fourfold treatment of samples in SPTFE suspension possess best protective properties. The obtained coatings decrease the corrosion current density (5.4 × 10−11 A cm−2) and wear (7.6 × 10−7 mm3 (N m)−1), and increase the polarisation resistance (1.7 × 109 Ω cm2) and impedance modulus (1.9 × 109 Ω cm2) by orders of magnitude in comparison with unprotected magnesium alloy and base PEO-coating. The highest value of contact angle (CA) has been obtained for coatings with triple application in telomeric solution. CA for such composite coatings attains (171 ± 2)°, as the result of multimodal roughness of the composite coating's surface.