Synthesis of polymeric surfactant containing bis-cationic motifs as a highly efficient acid corrosion inhibitor for C1018 carbon steel

The present study describes the synthesis and characterization of a poly(methyldiallylammonium chloride)-based surfactant containing bis-cationic motifs (9) through a series of reactions. The synthesized polymer 9 was characterized using FTIR and NMR spectroscopy and tested as a corrosion inhibitor for C1018 carbon steel (C1018 CS) in 1 M HCl using gravimetric weight loss, electrochemical, computational, and surface measurements. Polymer 9 serves as an excellent corrosion inhibitor and manifests 78.05%, 86.59%, and 92.68% inhibition efficiency values at 2, 5, and 50 ppm concentrations, respectively. Chemical analyses suggest that the inhibition efficiency of polymer 9 increases with an increase in the concentration and decreases with an increase in the temperature. The results indicate that polymer 9 becomes effective through adsorbing at the interface of C1018 CS following the Langmuir adsorption isotherm model. The outcomes of a polarization study reveal that polymer 9 behaves as a mixed-type inhibitor. Polymer 9 becomes effective by blocking the active sites responsible for the corrosion. The increase in the charge transfer resistance in the presence of polymer 9 also supported the above conclusion. The corrosion mitigation ability of polymer 9 through the adsorption mode was also demonstrated using scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) based surface investigations. Lastly, the mechanism of the adsorption of polymer 9 on the metallic surface was proposed based on the outcomes of DFT studies. A good agreement in the results of various experiments was observed.