Studies on corrosion-inhibiting performance of antithyroid drugs on mild steel in hydrochloric acid

The inhibitive performance of methimazole (MMI) and propylthiouracil (PTU), two antithyroid drugs on corrosion behaviour of mild steel in 0.1 M HCl solution, was investigated by means of electrochemical techniques and quantum chemical analysis. The increase in concentration shows a positive effect on inhibition efficiency while increase in temperature increases and decreases the efficiency of MMI and PTU, respectively. Inhibitor molecules directly adsorb at the surface on the basis of donor-acceptor interactions between the pi-electrons, sulfur and oxygen atoms and the vacant d-orbitals of iron atoms. According to the thermodynamic parameters, MMI and PTU adsorb chemically and physically, respectively. Adsorption of them on metal surfaces follows the Langmuir adsorption isotherm.