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.

Automated summary

The present study focuses on the synthesis and characterization of a polymeric surfactant containing bis-cationic motifs and its application as a corrosion inhibitor for C1018 carbon steel. The synthesized polymer showed excellent inhibition efficiency at different concentrations and temperatures. Various experiments revealed that the polymer works by adsorbing at the steel interface and acts as a mixed-type inhibitor by blocking active corrosion sites. The proposed adsorption mechanism was supported by DFT studies.