In this work, we studied the effect of inhibition of Sulfaguandine(SFG) against corrosion of the carbon steel in hydrochloric acid 1.0M HCl. For this, we used the weight loss measurements and electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Results obtained revealed that SFG performed excellently as a corrosion inhibitor for carbon steel in hydrochloric acid solution. Inhibition efficiency increases with increase in concentration of SFG. The efficiency reaches a maximum value of 95.71% at 5×10-3M. Electrochemical methods show that it acts as mixed-type inhibitor with predominant cathodic action. The SFG admits as the Langmuir adsorption. The thermodynamic activation parameters for the corrosion reaction were calculated and discussed in relation to the stability of the protective inhibitor layer. Attempt to correlate the molecular structure to quantum chemical indices was made using density functional theory (DFT).
