Corrosion, an age-old phenomenon, costs dearly; hence, possible technological means for corrosion mitigation/amelioration have almost been exhausted. Therefore, finding a disruptive mitigation approach is non-trivial, but any such discovery (e.g., graphene coatings) has immense social, commercial and technological implications. Graphene is attractive for numerous industrial applications. Among its several remarkable properties, graphene also possesses exceptional chemical resistance, outstanding impermeability to such chemicals that cause corrosion, and extraordinary toughness, which constitute the unique combination of characteristics for an ideal coating material for corrosion resistance. The review provides an in-depth critique of corrosion resistance of metals due to graphene coatings developed by chemical vapor deposition (CVD), identifies and critically assesses the associated challenges, and their demonstrated circumventions. CVD graphene has been widely developed on copper, nickel and their alloys; however, developing CVD graphene on common alloys, such as mild steel, is a non-trivial challenge. This review comprehensively discusses the compelling reasons of the challenge and evolution of an innovative prior surface modification of steel and its optimization, enabling successful CVD graphene coating on steel that conferred remarkable and exceptionally durable corrosion resistance. The prior surface modification is generic in nature and can be employed for CVD graphene on other engineering alloys. Schematic and example of robust corrosion resistance conferred to metallic substrate due to graphene coating: (a) Copper and nickel layers deposited on mild steel (MS), carbon and hydrogen atoms produced upon dissociation of hydrocarbon during CVD, and diffusion of carbon into Ni layer while the intermediate layer of Cu prevents (red arrow) the carbon from diffusing across to the mild steel substrate, (b) Graphene formation on the outermost layer of Ni upon CVD, which acts as an effective barrier and prevents (yellow arrow) the corrosive aqueous chloride solution from penetrating through to the metal surface, and (c) Durable corrosion resistance (expressed in impedance (kΩcm 2 )) of graphene coated mild steel in aggressive chloride solution. (a) Deposition of copper and nickel layers on mild steel, carbon and hydrogen atoms produced upon dissociation of hydrocarbon during CVD, and diffusion of carbon into Ni layer while the intermediate layer of Cu prevents (red arrows) the carbon from diffusing across to the mild steel substrate, (b) Graphene formation on the outermost layer of Ni during cooling after CVD, which acts as an effective barrier and prevents (red arrow) the corrosive chloride ions from penetrating through to the metal surfaces. (c) Durable (1008 h) corrosion resistance of graphene coated mild steel in chloride solution. • Ultrathin graphene coatings conferring remarkable and durable corrosion resistance is a disruptive approach. • Defects in CVD graphene layers may be counterproductive and addressing them is critical. • Developing multilayer graphene appears to be a practical approach to circumvention of the challenge. • Suitable prior surface modification enables successful development of graphene on mild steel.
Raman et al. (Sun,) studied this question.