Hydrophobic, anti-ice, wear- and corrosion-resistant C-(Ti)-PTFE coatings on Ti obtained by electrospark deposition using PTFE-impregnated graphite electrode

Titanium parts for marine and coastal infrastructure require protection from aggressive environment that lead to increased wear, corrosion and icing. To address these important issues, graphite-based coatings reinforced with titanium carbide and containing PTFE have been developed. Composite coatings were obtained by vacuum electrospark deposition using either a pure graphite (G) electrode or a porous graphite electrode impregnated with PTFE powder using both cathodic and anodic polarity. At cathodic polarity, the upper coating layer consists of mixtures of G + TiC (G electrode) and G + TiC + CF2 (G / PTFE electrode) phases. When changing polarity, coatings are obtained based on mixtures of Ti + TiC (G electrode) and Ti + TiF3 + −CF − (G + PTFE electrode) phases with a small amount of amorphous carbon on the surface. The as-deposited coatings were tested under conditions of simultaneous wear and corrosion in artificial seawater. The combination of G and TiC resulted in a hydrophobic (water contact angle (WCA) of 99°) corrosion-resistant (open circle potential (OCP) of 0.2 V versus −0.8 V for Ti) coating with a low coefficient of friction (0.1) and relatively low wear (2 × 10−5 mm3/Nm). The addition of PTFE increases hydrophobicity (WCA = 130°), significantly increases the freezing time of a water drop from 23 to 65 s, and reduces the ice adhesion strength from 0.52 to 0.38 MPa while maintaining tribocorrosion characteristics. The results obtained are important for the further development of wear-, corrosion-resistant, and anti-ice protective coatings.