Effects of electrophoretic deposited graphene coating thickness on the corrosion and wear behaviors of commercially pure titanium

Ti and its alloys have been exploited in various industrial sectors owing to its unique combination of properties. However, their poor corrosion and abrasion resistance behaviors lead to failure of industrial components. So, the purpose of this study is to improve both electrochemical and tribological properties of cp-Ti (Grade 2) by graphene coatings obtained through an elec- trophoretic deposition technique (EPD). In this study, two deposition times of 5 and 20 min were selected to examine the influence of coating thickness on coating properties. The surface morphology, phase purity, surface rough- ness, structure and adhesion strength of graphene coatings were investigated. The corrosion and wear resistance properties of bare Ti and graphene coat- ings were evaluated using electrochemical workstation and reciprocating type ball-on-plate tribometer respectively. The results revealed that the smooth and compact microstructure of thin graphene coating of thickness 2.16 μm ex- hibited superior corrosion resistance and lubricating properties (COF = ~0.02) compared to thick graphene coating of thickness 11.8 μm (COF = ~0.17). This may be ascribed to higher density of defects in terms of micro-porosities and voids in case of thick coating compared to that of thin coating which resulted in reduced barrier effect against corrosive solution and slight increment in its COF value. However, thick graphene coating displayed higher durability of its lubricity behavior and good wear resistance property due to the presence of less residual stress compared to thin graphene coating as characterized by X-ray diffraction analysis. Nevertheless, both graphene coatings demonstrated significant improvement in both corrosion and wear resistance properties of bare Ti substrate, thereby acting as a potential candidate to be used as a coating material for various industrial applications.