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 degrees) 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 x 10-5 mm3/Nm). The addition of PTFE increases hydrophobicity (WCA = 130 degrees), 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 tribo-corrosion characteristics. The results obtained are important for the further development of wear-, corrosion -resistant, and anti-ice protective coatings.