A unique anti-corrosion composite coating with CO2 gas barrier and acid resistance suitable for CCUS environment

In the process of carbon capture, utilization and storage (CCUS), carbon dioxide is in long-term contact with metal pipelines and devices. Therefore, in the CCUS environment the corrosion of carbon dioxide to metals limits the service life. Herein we have explored the failure of epoxy (EP) coating in the CO2 corrosion environment. Based on this, a unique g-C3N4-ESO-EP anti-corrosion coating suitable for CCUS conditions was prepared by using graphene-C3N4 (g-C3N4) nanosheet and epoxy silane oligomer (ESO) one-step method. The semiconductor g-C3N4 prepared by the secondary thermal stripping method provides plentiful CO2 adsorption sites and prevents the diffusion of corrosive ions (gathered state CO2, CO32 , HCO3 ?, H+) in the EP coating. The CO2 gas permeability of g-C3N4-ESO-EP film (with thickness of 100 & mu;m) is approximately 45.94% lower than that of EP film. After immersion in 1.0 M acid corrosion environment, the protection efficiency of g-C3N4-ESO-EP coating is 99.99%. After adding ESO, the "bridging effect" formed at the interface reduces the interface defects between the resin and the nano-sheet, and synergistically enhances the adhesion between the coating and the substrate. The gC3N4-ESO-EP coating has passed the test of severe simulated CCUS corrosion environment (4 days in 3.0 MPa CO2 and 3.5 wt% NaCl solution). The |Z|0.01Hz value of g-C3N4-ESO-EP coating after immersion in 3.5 wt% NaCl solution for 120 days maintained 1.73 x 1011 O cm2, indicating the coating has long-term corrosion resistance. This work provides a new and simple method to improve the CO2 resistance of EP coating and reveals the importance of functional composite coating for metal protection in CCUS process.