Corrosion mechanism and resistance of g-C3N5@PDA nanosheets modified epoxy-coated carbon steel

Nitrogen-rich carbon nitride (g-C 3 N 5 ) nanosheets were modified with polydopamine (PDA) and then incorporated into an epoxy resin (EP) matrix to create a g-C 3 N 5 @PDA modified epoxy (GP/EP) coating. The phase composition, microstructure, and mechanical properties were analyzed using X-ray diffraction, scanning electron microscopy, and nano-indentation. The corrosion behavior was investigated by applying the coating to a steel plate and immersing it in a NaCl solution for 20 days using electrochemical impedance spectroscopy and potentiodynamic polarization tests. Molecular dynamics simulations were also conducted to elucidate the corrosion mechanism. The results indicated that the hardness and elastic modulus of the epoxy coating increased from 0.02 GPa to 0.26 GPa and from 0.92 GPa to 2.90 GPa, respectively, after the modification of g-C 3 N 5 nanosheets with PDA. Additionally, the corrosion current density of the GP/EP-coated steel plate was measured at 0.51 μA/cm 2 , which is approximately 17 times lower than that of the EP-coated plate when immersed in a 3.5 wt% NaCl solution.