Corrosion Inhibition of Mild Steel by Using Sulpha Drugs in Phosphoric Acid Medium: A Combined Experimental and Theoretical Approach

The corrosion inhibition effect of Sulfacetamide and sotalol on the mild steel has been investigated in 1M H3PO4 acid medium. The inhibiting effect was investigating using weight loss measurement and quantum chemical method. The obtained results revealed that both inhibitors inhibited the mild steel corrosion in the phosphoric acid solution. The inhibitors showed more than 90% inhibition efficiency at optimum concentration. Sulfacetamide shows inhibition efficiency of 94.22 whereas sotalol shows efficiency of 91.40 at optimum concentration. Results obtained exposed that inhibition occurs through adsorption of the drugs on mild steel surface without modifying the mechanism of corrosion process obeying the Langmuir adsorption isotherm. Density functional theory (DFT) has been used to determine the relationship between molecular configuration and their inhibition efficiencies. The order of inhibition performance obtained from experimental results is successfully verified by DFT. Scanning electron microscopy (SEM) studies of the mild steel surfaces established the presence of a protective adsorbed film.