Development of graphene-based anticorrosion coatings

Abstract

The phenomenon of corrosion has been the subject of research for years driven by the demand from industries that utilize steel structures. The impact of corrosion-related economic losses is exacerbated in oil & gas industries that process ever increasing acidic streams of hydrocarbons. The extraction and processing of hydrocarbon resources associated with acidic gases (H 2S, SO2 & CO2) is a common problem in Gulf countries owing to the heavy dependence on oil & gas generated revenue. It has been estimated that the annual cost of corrosion in the UAE was the second highest among the GCC countries [1, 2]. Research has recently shifted towards nanomaterials to augment the anticorrosion capacity of organic coatings. Graphene, a one atom thick honeycomb structure of sp2 hybridized carbons possesses unique characteristics. The properties of graphene make it an excellent candidate for the development of environmentally benign anticorrosion coatings with extended service lifetimes. In this work, graphene-based anticorrosion coatings were synthesized and their anticorrosion performance was investigated. Different coating formulations were produced and tested to explore the prospects of graphene fillers in two polymer systems. The two polymer systems selected were Poly(methyl methacrylate) and Diglycidyl Ether of Bisphenol A (BADGE). Graphene nanosheets with a high carbon-to-oxygen ratio were used as well as Graphene oxide (GO) having a relatively low carbon-to-oxygen ratio. The corrosion resistance of the produced coatings was studied by Electrochemical Impedance Spectroscopy (EIS) and corrosion susceptibility was evaluated by Linear Polarization (LP) tests. Other characterization techniques were employed to gather more information about the synthesized nanocoatings including Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The electrical conductivity of the produced coatings was also measured and their adhesion evaluated as per the ASTM-D3359 standard. The coatings produced exhibited strong adhesion and improved anticorrosion performance with increased graphene and graphene oxide loadings. The PMMA coating reinforced with 5 wt% graphene possessed the highest impedance. On the other hand, it was found that loadings as low as 1 wt% graphene oxide significantly enhanced the anticorrosion performance of the crosslinked epoxy resin. The use of 5 wt% GO in the epoxy matrix however caused a slight increase in the corrosion resistance of the coating. The corrosion resistance of the synthesized nanocoatings was attributed to the low wettability and barrier effects imparted by the dispersed graphene filler. The corrosion resistance of the GO reinforced epoxy polymer was attributed to the formation of a tortuous diffusion pathway. Despite the hydrophilic nature of GO, the oxygen functionalities permitted stronger and more stable interactions with the host epoxy polymer which led to enhanced barrier properties.

Date of Award	2015
Original language	American English
Supervisor	Vikas Mittal (Supervisor)