Experimental evaluation of new organic compounds as corrosion inhibitors for mild steel in hydrochloric acid

Mild steel is one of the most widely used construction materials that finds various applications in industry owing to its exceptional mechanical properties and low cost. However, hydrochloric acid is widely used as an efficient pickling agent in steel industries to remove rust and scales, but it accelerates steels corrosion rate. Corrosion inhibitors are one of the most effective methods used to reduce mild steel corrosion in acidic media. In this study, new synthetics organic compounds L1, L2 and L3 were examined as corrosion inhibitors for mild steel in 1 M hydrochloric acid solutions using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). For the examined concentrations range, it was observed that the inhibition efficiency increased with increasing L1 and L2 concentrations and decreased with increasing L3 concentration. The maximum efficiency of 69% was achieved at 300 ppm of L2 at room temperature. Based on polarization studies, all the compounds were found to behave as anodic type inhibitors. SEM micrographs showed that the used inhibitors slowed down the corrosion of the surface with fewer cracks and pits observed. The quantum chemical parameters were calculated and showed a good agreement with the experimental results.