Corrosion protection mechanisms of graphene oxide-reinforced polypropylene coating for mild carbon steel by advanced molecular dynamics simulations with emphasis on resistance to water and chloride ion penetration

Polypropylene can be used as a raw material for manufacturing corrosion-resistant coatings to protect the surface of the mild carbon steel substrate. To improve the properties of polypropylene (PP), graphene oxide (GO) can be added to the coating. In this research, molecular dynamics (MD) simulations were employed to evaluate the effect of GO additives on the PP coating using COMPASS Force-Filed of the Forcite module. The results of molecular modeling, such as mean square displacement (MSD), diffusion coefficient, concentration profile, and gyration radius (Rg), revealed that the permeability of corrosive agents, including water molecules and chloride ions in the composite coating (PP/GO), is much lower than pure one (PP). In addition, by reducing the surface energy from 77 to 68 mJ/m2, the water contact angle (WCA) is improved from 150◦ for the pure PP coating to 170◦ for the composite one. It can also be due to an 18% increase in system compaction in the presence of GO. In the other hand, the free fraction volume (FFV) in the presence of GO is reduced by about 4%. The adhesion of the coating to the mild carbon steel substrate has also been ameliorated by 38% for the PP/GO coating compared to the pure PP. Therefore, most of the simulated parameters reported the positive effects of compositing PP with GO.