Enhancement in the corrosion resistance behaviour of amorphous Ni-P coatings by incorporation of graphene

In the current study, amorphous nickel-phosphorus-graphene (Ni-P-G) composite coatings were electroplated on mild steel substrate. Coatings were electroplated from nickel sulphate bath containing phosphorus acid and exfoliated graphene in amounts of 50 mg/l, 100 mg/l, 150 mg/l, and 200 mg/l. Phase constitution, composition, surface morphology and corrosion parameters were investigated as a function of the graphene content. Experimental results exhibited that Ni-P and Ni-P-G composite coatings possessed improved corrosion resistance than the mild steel substrate and addition of graphene enhanced the corrosion resistance performance when compared to the pristine coating. It was observed that an optimum exists with respect to the amount of graphene dispersed in the electrolyte bath for achieving high anti-corrosion property from the coating produced using the respective plating bath. Lower amount of graphene in dispersion produced uniform surface morphology which acted along with the graphene impermeability to yield high corrosion resistance performance. Higher quantity of graphene in dispersion, on the other hand, caused their agglomeration thus producing rough and defective surface morphology which along with non-uniform distribution of graphene yielded higher corrosion rates.