Electrochemical behavior of nanostructured graphene nickel phosphorus composite coating on copper

Abstract

The present work is focused on the effects of graphene addition on the electrochemical performance of environmentally benign nanostructured graphene–nickel–phosphorus composite coating (G–NiP) on copper developed by electroless deposition. The coatings were developed using no external dispersing agents and toxic reductant such as hydrazine. The electrochemical corrosion behavior of the coating was investigated using potentiodynamic polarization (PDP) measurement. The anodic polarization curves of the Ni–P coating on copper (Cu–NiP) show two distinct active–passive regions and an oxidation peak, whereas graphene Ni–P coating (Cu–G–NiP) shows almost passive behavior. For Cu–NiP at critical pitting potential (Ec), the passivation breaks indicating initiation of pits, whereas Cu–G–NiP shows the absence of Ec. The PDP results also demonstrate the enhanced corrosion resistance property of the Cu–G–NiP with corrosion inhibition efficiency of 95%. The electrochemical impedance spectroscopy was used to analyze the physical and electrochemical process occurring at various interfaces and to study the influence of graphene in the coating under a corrosive environment. The higher density of micropores is evident from the FESEM image of Cu–NiP, whereas comparatively fewer micropores are observed in the case of Cu–G–NiP after the electrochemical test. This study also reveals that the addition of graphene in the Ni matrix inhibits pore creation and pit formation leading to better intactness of the coating.