Effects of Carbon Allotrope Type on Microstructural and Electrochemical Properties of Ni-C Nanocomposite Coating Prepared by Pulse-Reverse Electrodeposition Method

In this study, the pulse-reverse electrodeposition method was utilized to fabricate Ni reinforced with various carbon allotropes (Carbon Nanotube (CNT), Graphite (Gt), and Graphene (Gr)) coatings. The impact of carbon addition and type on the microstructural features and electrochemical behavior of the Ni coating was studied. Microstructural characterization was conducted using Field-Emission Scanning Electron Microscopy, Atomic Force Microscopy, X-ray diffraction pattern, and Raman spectroscopy. The findings revealed a transition from a porous pyramid-like structure to a denser and uniform microstructure with addition of reinforcing particles. Additionally, Atomic Force Microscopy investigations demonstrated reduced surface roughness for CNT, Gt, and Gr inclusions, with Ni-Gr displaying the lowest roughness. Evaluation of the electrochemical properties through Electrochemical Impedance Spectroscopy and polarization measurements showed a 30%, 54%, and a remarkable 60% enhancement in corrosion protection for Ni reinforced with CNT, Gt, and Gr coatings, respectively. Polarization tests confirmed a substantial reduction in corrosion current density, from 6.2 µA/cm² for Ni coating to 1.9, 0.4, and 0.1 µA/cm² for Ni-C coatings with CNT, Gt, and Gr carbon allotropes, respectively, indicating the exceptional corrosion resistance of Ni-Gr composite coating prepared by the used method.