Synthesis of Gemini cationic surfactants based on natural nicotinic acid and evaluation of their inhibition performance at C-steel/1 M HCl interface: Electrochemical and computational investigations

Herein, we prepare effective Gemini cationic surfactants (CSII, CSIV) and characterize them using FT-IR and 1HNMR spectroscopy. The adsorptive properties of CSII and CSIV at HCl/air and C-steel/HCl interfaces were examined with surface tension and electrochemical parameters, respectively. The critical micelle concentration (CMC) of the CSII and CSIV indicated their adsorption affinity at the HCl/air interface. Where, aliphatic chains increase surface coverage percentage and aid in surfactant adsorption. The electrochemical parameters of C-steel in 1 M HCl were studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) at different temperatures. The charge transfer resistance of the C-steel electrode was enhanced from 28.2 Omega.cm2 to 770.79 and 831.45 Omega.cm2 after adding 5 x 10-4 M of CSII and CSIV, respectively. Both CSII and CSIV act as mixed inhibitors with inhibition performance exceeding 97% due to their highly adsorption affinity. The chemical adsorption affinity of these compounds is suggested by the higher adsorption energy (Delta G*ads) values (>-40 kJ mol-1) according to the Langmuir isotherm model. The theoretical calculations including DFT, and Monte Carlo simulation (MCs) provide insight into the relationship between corrosion inhibition and molecular structure, where the calculated parameters agree with the experimental results.

Automated summary

In this study, effective Gemini cationic surfactants (CSII, CSIV) were synthesized and characterized. The adsorptive properties of CSII and CSIV at HCl/air and C-steel/HCl interfaces were investigated using surface tension and electrochemical parameters. The results showed that CSII and CSIV have high adsorption affinity at the HCl/air interface, with aliphatic chains promoting surfactant adsorption. Electrochemical impedance spectroscopy and potentiodynamic polarization revealed that CSII and CSIV act as mixed inhibitors, significantly enhancing the charge transfer resistance of C-steel in HCl. Theoretical calculations and simulations supported the experimental findings, demonstrating the relationship between corrosion inhibition and molecular structure.