Sulfur-doped graphitic carbon nitride (S-g-C3N4) as an efficient corrosion inhibitor for X65 pipeline steel in CO2- saturated 3.5% NaCl solution: Electrochemical, XPS and Nanoindentation Studies

The present study reports the role of sulfur-doped graphitic carbon nitrides (S-g-C3N4) as a self- assembly corrosion inhibitor for X-65 steel in 3.5% NaCl solution enriched with CO2. The S-g-C3N4 was synthesized via simple pyrolysis and polymerization route. Detailed physiochemical characterization was carried out using XRD, Raman, FTIR, UV, and XPS analysis. Surface analysis such as FE-SEM and AFM studies reveals a uniform coating of S-g-C3N4 over the steel surface. Electrochemical techniques were adopted to investigate the efficiency of S-g-C3N4 on steel corrosion mitigation. Maximum inhibition efficiency of 98% and 94% at concentration of S-g-C3N4 (0.3 wt%) for polarization and impedance methods were achieved. Also, the DFT and MD simulation studies evidenced that S-g-C3N4 forms a protective layer over the steel surface. The excellent inhibition efficiency of the S-g-C3N4 is due to the presence of sulfur heteroatom thus has more affinity towards steel surface. This sulfur doped g-C3N4 could open up new opportunities in corrosion and materials protection area.