Spray pyrolytic layer modification of glass reinforced polymer substrate using graphene and graphite blend

Conveyance of crude oil is usually done using carbon steel pipes due to their high strength and electrical conductivity. However, carbon steel is prone to severe corrosion both internally and externally. Hence, it becomes necessary to develop suitable, lightweight, cost-effective, and electrically conductive materials that can serve as alternatives to carbon steel pipeline sections in the oil and gas industry. This study investigates the adaptability of nanoparticle-sized graphene and graphite-coated GRP (Glass Reinforced Polymers) as substitutes for steel in corrosion control and pipeline rehabilitation. The coating process employed low-temperature spray pyrolysis (50–60 °C) to deposit nanoparticle graphene and carbonized graphite on GRP substrates of 50 × 10 × 2 mm dimensions. Single- and double-layer coatings were applied using graphene-graphite blend ratios of 1:0.5 and 1:1. Electrical resistance was measured using an LCR meter, from which electrical conductivity was calculated. The samples were characterized using SEM, XRD, FTIR, and thermal analysis (TGA), while hardness was evaluated using the Rockwell method (HLD). Results showed that the GRP sample with a double-layer 1:1 graphene: graphite blend had the highest hardness (59.33 HLD), while the GRP with single-layer graphene coating recorded the highest electrical conductivity of 1.8×10⁻⁶ S/m. TGA revealed improved thermal stability in GRP samples, with glass transition temperatures (Tg) near 400 °C. Image J analysis of SEM images showed that moderate grain sizes (2–4 μm²) correlated strongly with improved wear resistance and conductivity. Wear tests confirmed that the 1-0.5D hybrid sample had the lowest wear rate and volume loss, while performance indexing ranked G-S (Graphene Single Layer) as the best all-around GRP performer. Tensile testing demonstrated significant improvements in strength, stiffness, and ductility, with tensile stresses above 23 MPa in coated GRP samples. A mathematical model was also developed to predict electrical conductivity as a function of coating thickness. Additionally, CP modelling demonstrated that introducing a non-conductive GRP section in an ICCP-protected pipeline causes localized under protection, which can be mitigated using optimized bypass wire design. In conclusion, this study establishes that graphene and graphite coatings, applied via spray pyrolysis, enhance the electrical, mechanical, and thermal properties of GRP. Among these, GRP composites coated with graphene—especially G-S and 1-0.5D—offer a promising, multifunctional alternative for steel in pipeline repair, leak mitigation, and corrosion control applications in the oil and gas industry.