Permeation behavior of salt solution through g-C3N5/epoxy coatings: Insights from molecular dynamics simulation

Abstract

Organic coatings with a physical barrier network can effectively inhibit the corrosion of carbon steel. In this study, epoxy coating modified with one pristine nitrogen-rich carbon nitride (g-C3N5-PRI) nanosheet and two functional group-modified g-C3N5 (i.e.,g-C3N5-NH2 and g-C3N5-COOH) nanosheets were developed, and their permeation behaviors in sodium chloride (NaCl) solution were investigated by molecular dynamic simulation. In addition, the dynamic behavior and distribution of NaCl solution particles between the three nanosheets and the epoxy resin chain were also studied. The results show that the number and type of hydrogen bonds formed between the nanosheets and water molecules are the decisive factors affecting the penetration of NaCl solution in the coating. The two functional groups of nanosheets play an important role in impeding penetration of NaCl solution, and g-C3N5-COOH nanosheet performs better than g-C3N5-NH2 nanosheet. The solution particles captured in the modified coatings are blocked on the surface of the nanosheets, which is the main reason for the decrease of the adhesion between the nanosheets and the epoxy coating matrix.