Comparison of in situ and ex situ reduced graphene oxide reinforced electroless nickel phosphorus nanocomposite coating

Highlights: • First kind of electroless nickel phosphorous (EN) reduced graphene oxide (rGO) coatings. • Change in preferential orientation of grain growth of heat treated in situ EN-rGO coating. • Better corrosion resistance of in situ EN-rGO coating. • 2 stages of reduction of Graphene (GE) to GO, during - coating and heat treatment. • Soft nature of GO for similar to polymer from low hardness of EN-GO coating. - Abstract: Electroless nickel-phosphorus (EN)–reduced graphene oxide (rGO) composite coating was carried out to compare the ex situ route of reinforcement of reduced GO in EN coating (EN-rGO) and in situ route of reinforced of rGO in EN coating (EN-GO). The coatings were characterized using X-ray diffraction (XRD) and attenuated total reflectance infrared spectroscopy (ATR-IR) for phase determination and to show the presence of reinforcement of rGO in the coatings respectively. ATR-IR spectra indicated that GO was chemically reduced in situ while deposition of EN-GO composite and thermal reduction during its heat treatment. XRD pattern of heat treated EN-GO coating show the change in preferred orientation of nickel deposit. Upon heat treatment, the hardness of EN and EN-GO and EN-rGO deposits increased while the corrosion resistance decreased except for EN-GO coating. The hardness of EN-rGO and EN-GO coating is approximately half the value of EN deposit. The electrochemical polarization studies indicated that EN-GO deposit was corrosive resistant than EN-rGO and EN deposit