Revisiting graphene–polymer nanocomposite for enhancing anticorrosion performance: a new insight into interface chemistry and diffusion model

Abstract

Graphene is impermeable to all molecules and has high chemical stability, which makes it an excellent anticorrosion coating for metals. However, current studies have indicated that galvanic coupling between graphene and a metal actually accelerates corrosion at the interface. Due to the insulating nature of polymers, graphene-polymer composite coatings with a strong interaction between the filler and the polymer matrix are an alternative means of addressing this issue. Nevertheless, such coatings require well-dispersed graphene flakes to lengthen the diffusion paths of gases or liquids, while preventing the formation of a conducting network from graphene to the metal. The difficulty in preparing such coatings was mainly due to problems with the control of the assembled phase during interfacial reactions. Herein, the interactions between the filler and the polymer were found to be a key factor governing anticorrosion performance, which has scarcely been previously reported. The advantage of graphene as a filler in anticorrosion coatings lies in its dispersibility and miscibility with both the casting solvent and the polymer. Electrochemically exfoliated graphene (EC-graphene) with appropriate surface functionalities that allow high miscibility with waterborne polyurethane (PU) and hydrophobic epoxy has been found to be an ideal filler that outperforms other graphene materials such as graphene oxide (GO) and reduced graphene oxide (rGO). Furthermore, a bilayer coating with EC-graphene additives for PU over epoxy has been found to reduce the corrosion rate (CR) to 1.81 × 10-5 mm per year. With a graphene loading of less than 1%, this represents the lowest CR ever achieved for copper and steel substrates and a diffusion coefficient that is lower by a factor of nearly 2.2 than that of the pristine polymer. Furthermore, we have shown that by controlling the amount of graphene loaded in the polymer galvanic corrosion favored by the formation of an interconnected graphene percolation network can successfully be limited. The present study, together with a facile and eco-friendly method of nanocomposite synthesis, may pave the way toward practical applications in the development of graphene-based anticorrosion coatings.

An alternative synthesis route to graphene oxide: influence of surface chemistry on charge transport in epoxy-based composites

“…It should be noted that the small S content seen in both GO and mGO is consistent with published data, where the effect has been attributed to covalently bonded sulphates or absorbed sulphuric acid [55]. In comparison, rGO typically shows C/O values of * 7.5 [38] but can reach up to * 12 [54]. Furthermore, the oxygen content for GNP is usually around 7% [56] or lower [57].…”

“…Consequently, in order to avoid such phenomena, EG/GNP or reduced GO (rGO), should be ideally used, which exhibit reduced defect contents and do not disrupt the epoxy crosslinking. Alternative methods such as electrochemical exfoliation [38][39][40] could be used, in order to tailor the oxygen content. The downside (apart from poor compatibility for the two former systems) is that the production of such systems involves multistep processing/synthesizing routes, which both adds complexity and reduces yields.…”

Neodymium-decorated graphene oxide as a corrosion barrier layer on Ti6Al4V alloy in acidic medium

“…Moreover, the GO + Nd coating OCP values largely shied to the less negative potentials with values ranging from À0.20 to À0.25 V, indicating that the coating does not allow the corrosive ions to penetrate to the alloy surface. [60][61][62][63][64][65] In Fig. 9, the potentiodynamic polarization behaviour of the epoxy and GO + Nd coatings are shown.…”

“…6 Dutta et al reported a graphene oxide-polymer composite material that reinforced the corrosion inhibition in the mild steel, which was attributed to the improved hydrophobicity due to the polymer matrix. 7 Furthermore, Huh et al reported that the acetone-derived graphene oxide acts as a corrosion inhibitor on copper in a 3.5% NaCl medium. 8 Maia et al reported that silica nano particles have been used as a corrosion barrier for an aluminium alloy in salt environments.…”

Protection of Mild Steel by Waterborne Epoxy Coatings Incorporation of Polypyrrole Nanowires/Graphene Nanocomposites

“…A few slight increases were observed for Blank and EPPyNG1 after immersion several days, probably due to the accumulation of corrosion products [23]. The potential of EPPyNG3 coating dropped sharply to −0.70 V after immersion 20 days, revealing that excess graphene was detrimental to the anticorrosion property [40]. The potentiodynamic polarization tests were carried out to study the anticorrosion performance of EPPyNG composites coatings.…”