Surface modification of mild steel to circumvent challenges in chemical vapour deposition of graphene coating for durable corrosion resistance

Graphene possesses unique combination of characteristics (i.e., inertness, impermeability and toughness) to qualify as ideal coating material for corrosion resistance, and graphene coatings on nickel and copper have been shown to provide excellent and durable corrosion resistances. However, growing graphene directly on mild steel by chemical vapour deposition (CVD), is prohibitively challenging due to high solubility of carbon in mild steel at high temperatures. The non-trivial challenge was circumvented through surface modification of steel by electroplating with Cu and Ni, accounting for the critical consideration, i.e., the inter-diffusivity of iron in nickel or copper. However, the key finding was that the undesirably high thicknesses of the electroplated Cu and Ni layers were detrimental, and optimization of their thicknesses was essential for successful deposition of the required quality graphene. The optimised thicknesses were derived on the basis of the fundamental diffusion calculations. The uniform multi-layered graphene coating on the suitably modified mild steel surface provided remarkable corrosion resistance in an aqueous chloride solution, and electrochemically validation of the corrosion durability for extended exposure (>1000 h) was characterised.