Adsorption Study of Doxycycline to Protect the Mild Steel Surface from Sulphuric Acid Solution

The ability of doxycycline to prevent corrosion of mild steel in 0.5 M sulphuric acid was investigated by using weight loss measurements, polarization resistance, Tafel polarization, and EIS (Electrochemical Impedance Spectroscopy). Doxycycline was a powerful inhibitor for mild steel corrosion, with an effectiveness of 99.2 % at 4.5×10-4 M. The thermodynamic parameters were computed and discussed to evaluate the process of inhibition. The drug fits the Langmuir isotherm. Potentiodynamic polarization studies indicate that it acts as a mixed-type inhibitor. The Electrochemical impedance spectroscopy reveals that raising the concentration of doxycycline amplifies the charge transfer resistance while dropping the double-layer capacitance. Surface morphology investigations were done with atomic force microscopy (AFM) on metal surfaces.