Synthesis and experimental study of new coumarin derivatives as corrosion inhibitors for carbon steel surface in 3.5% NaCl

Using organic compounds is a typical way to prevent corrosion on carbon steel. The current study aims to evaluate the inhibition efficiency of different coumarin sulfonamides that contain imine groups. These compounds were synthesized by reacting 4,7-dimethyl coumarin with chlorosulfonic acid under cold conditions resulting in 4,7-dimethyl-6-chlorosulphonyl coumarin. Then, the appropriate sulfonohydrazide was obtained by reacting a chlorosulphonyl coumarin derivative with hydrazine hydrate. Finally, Schiff base derivatives were created by treating the resulting sulfonohydrazide with various aromatic aldehydes. The electrochemical polarization method was used for evaluating corrosion. Atomic force microscopy and field emission scanning electron microscopy examined the alteration in surface morphology to identify which of the manufactured compounds had the highest level of corrosion resistance. Rf, FTIR, 1H NMR, and 13C NMR spectroscopy were used to figure out the structures of the synthesized compounds, which were in line with what had been proposed. All synthesized compounds exhibited corrosion resistance in NaCl solution at different temperatures. The 4,7-dimethyl-N-4-nitrobenzylidene-2-oxo-2H-chromene-6-sulfonohydrazide [M3] compound provides the best corrosion resistance of carbon steel in a 3.5% NaCl solution at the same temperatures. These findings were supported by the results of AFM, FESEM, EDS, and XRD.