Experimental Investigation of Corrosion Inhibitor Performance for Carbon Steel in Industrial Hydrochloric Acid Pickling

Carbon steel pickled with hydrochloric acid can suffer from considerable dissolution, greater acid consumption, and poor surface quality. This research assessed the effectiveness of a commercially available corrosion inhibitor for carbon steel pickled under industrially representative conditions (13.2 wt.% (weight percent) HCl (hydrochloric acid), 28 g·L−1 dissolved iron, 80–85 °C, and brief periods of contact with pickling solution at 32, 56, and 113 s). Mass loss and inhibitor efficiency (IE) were determined through gravimetric analysis under dynamic pickling conditions using varying concentrations of inhibitor and duration of contact. The results indicate that the extent of mass loss decreases considerably with increasing inhibitor concentration. The optimal concentration was found to be 0.6 g·L−1, giving an inhibitor efficiency greater than 90% under preliminary screening conditions and 70–79% under industrially relevant conditions, with further increases in inhibitor concentration providing little additional protection, suggesting nearly complete surface coverage. Observations of the surface showed better pickling uniformity and brilliance. The optimal inhibitor concentration resulted in reductions of 21% in inhibitor usage and over 27% in acid regeneration compared to a non-optimized inhibitor dosage.