TiO₂ - graphene reinforced epoxy coatings for enhanced wear and corrosion protection

Developing durable multifunctional coatings is essential for protecting metal substrates exposed to combined mechanical and corrosive environments, where conventional epoxy systems often fail due to limited hardness and inadequate long-term barrier performance. This study develops TiO₂–Graphene reinforced epoxy coatings on Al6061 alloy using a sol–gel assisted dip-coating method to harness the complementary advantages of ceramic rigidity and graphene’s impermeable network. The influence of TiO₂ (0.5–2 wt.%) and graphene (0.1–0.5 wt.%) was evaluated through XRD, SEM-EDS, surface profilometry, microhardness testing, pin-on-disc tribology (ASTM G99), and electrochemical measurements (PDP and EIS) in 3.5 wt.% NaCl. The hybrid coating (E–TiGr) exhibited a dense, defect-free microstructure with uniform nanoscale dispersion, resulting in a hardness increase from 21.6 HV (neat epoxy) to 42.1 HV. Wear rate decreased from 1.28 × 10⁻⁴ to 0.51 × 10⁻⁴ mm³·N⁻¹·m⁻¹, accompanied by a lower coefficient of friction (0.41). Electrochemical tests showed a shift toward a more positive corrosion potential (−0.588 V) and a reduced corrosion current density (1.1 × 10⁻⁶ A·cm⁻²), corresponding to ~72% protection efficiency. EIS confirmed the highest charge-transfer resistance (~5.8 kΩ·cm²), indicating restricted ionic transport. Overall, the TiO₂–Graphene hybrid epoxy coating demonstrates significantly improved mechanical integrity and corrosion resistance, highlighting its potential for marine, automotive, and structural applications.