Corrosion inhibition of mild steel in acidic medium by some sulfa drugs compounds

The inhibiting effect of four sulfa drugs compounds (e.g. sulfaguanidine, sulfamethazine, sulfamethoxazole and sulfadiazine) on mild steel corrosion in 1.0 M HCl solutions were evaluated using both galvanostatic polarization and weight loss techniques. All the examined sulfa drug compounds reduce the corrosion of mild steel. Among the compounds studied, sulfadiazine exhibited the best inhibition efficiency and sulfaguanidine the lowest. The inhibition efficiency goes through a maximum for sulfaguanidine while it increases continuously with concentration to a limit with sulfadiazine, sulfamethoxazole and sulfamethazine respectively. Galvanostatic polarization measurements indicate that all the examined compounds are of mixed inhibitor type with predominant cathodic effectiveness. Moreover, the results revealed a better performance for these compounds as corrosion inhibitors in HCl than in H₂SO₄ solutions. Also, the corrosion inhibition mechanism is discussed.