Improved anticorrosive and tribological performance of Ti-6Al-4V alloys via a mussel-inspired graphene/phenol-formaldehyde resin nanocomposite coating

In the present study, a mussel-inspired composite film containing an interlayer of mussel protein and a top layer of graphene/phenol-formaldehyde resin composites deposited by cathodic electrophoresis is designed to protect Ti-6Al-4V alloys from corrosion and wear. The impedance modulus of bare Ti-6Al-4V substrates at the low frequency of 0.01 Hz is increased by more than 3 orders of magnitude and the corrosion rate is reduced by 2–3 orders of magnitude with the protection of designed films. Also, it exhibits a long-term anticorrosion performance to salt fog and can avoid acid corrosion. The mussel protein not only acts as a corrosion inhibitor to improve the anticorrosion properties by coordination bonds with titanium dioxide but also serves as a separating layer to shield the galvanic reaction between the graphene and metal. The nanocomposite top layer plays a role in physical isolation from corrosive medium and preventing the oxidation of mussel protein. Although the addition of soft phase (resin and protein) sacrifices the excellent lubricant effect of graphene nanosheets, the designed coating can reduce the COF of Ti-6Al-4V alloys from 0.71 to 0.31 with a low wear rate of 1.07 × 10−4 mm3/N·m.