Effect of carbonaceous reinforcements on anticorrosive and magnetic properties of Ni-Cu based composite coatings prepared by pulsed electrodeposition

Magnetic and anticorrosive properties of Ni-Cu alloy-based composite coatings prepared by pulsed electrodeposition reinforced with CNT (Ni-Cu-CNT), graphene (Ni-Cu-G), and diamond (Ni-Cu-D) have been assessed in the current work. The corrosion behavior of the composite coatings was evaluated in a 3.5% NaCl corrosive medium. Linear polarization test performed within +/- 10 mV with respect to open circuit potential (OCP) unveiled that graphene added coatings exhibited maximum polarization resistance (~13.1 k omega cm(2)) followed by the Ni-Cu-D (~9.1 k omega cm(2)), the Ni-Cu-CNT (~8.3 omega cm(2)), and the Ni-Cu with a minimum resistance of ~4.2 k omega cm(2). Electrochemical impedance spectroscopy tests performed with a signal perturbation of +/- 10 mV with respect to OCP and frequency sweep from 10(5) Hz to 10(-2) Hz elicited maximum film resistance of ~32 k omega cm(2) for the Ni-Cu-G coating, which could be attributed to the high area to volume ratio, alpha ~134/m, of graphene nanoflakes inducing strong particle-matrix interaction and to the formation of micro galvanic cell between the graphene particles and the Ni-Cu matrix where the surface was covered predominantly with graphene, eventually lowering the corrosion rate to 5.91 MPY. For Ni-Cu-D coating, the uniform dispersion of diamond particles prohibits localized corrosion. In contrast, agglomeration of CNTs in Ni-Cu-CNT causes ~50% reduction in corrosion resistance compared to diamond reinforced coating. However, corrosion resistance of CNT grafted coating was around 2.5 times higher than Ni-Cu (~4.2 k omega cm(2)), which can be imputed to the filling of the pores, cracks, and crevices by CNT fibers. The hysteresis loops of Ni-Cu composite coatings traced by a vibrating sample magnetometer indicated that CNT incorporation enhanced the magnetic saturation to ~1.89 Am-2/kg from ~0.84 Am-2/ kg (Ni-Cu) and maximum coercivity of ~110 Oe (~78.91 Oe for Ni-Cu). However, graphene and diamond addition has negligible effect on the magnetic properties of the coated systems. The enhanced anticorrosive and magnetic properties of proposed coating designs consisting of Ni-Cu matrix with carbonaceous reinforcements impart multifunctionality to the system. The marine industry can successfully adopt the proposed coating systems to protect propellers shafts, ship hulls, and specialty sensors.

Automated summary

This study evaluated the magnetic and anticorrosive properties of Ni-Cu alloy-based composite coatings reinforced with CNT, graphene, and diamond. The results showed that the addition of graphene significantly improved the corrosion resistance, while the incorporation of CNT enhanced the magnetic properties of the coatings.