Corrosion inhibition and mechanism of mild steel in hydrochloric acid by ceftriaxone and amoxicillin

Abstract

Corrosion inhibition of mild steel in 1 mol/L HCl by amoxicillin and ceftriaxone in the concentration range of 1.00x10(-5)-1.00x10(-2) mol/L has been studied using weight loss, electrochemical potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and quantum chemistry tests at 298 K. The weight loss experiment showed that the inhibition efficiency increased with amoxicillin and ceftriaxone concentrations to attain the maximums of 80.3% and 94.1%, respectively at 1.00x10(-2) mol/L. Potentiodynamic polarization indicated that amoxicillin and ceftriaxone acted as mixed-type inhibitors but mainly inhibited cathode hydrogen evolution reaction for mild steel in 1 mol/L HCl. The electrochemical impedance spectroscopy (EIS) demonstrated the inhibitors covered the active points of metal surface to inhibit corrosion. The absorption of both inhibitors on the mild steel surface was found to follow Langmuir adsorption isothermal and dominantly involve chemical adsorption at 298 K. Scanning electron microscopy (SEM) confirmed both of the inhibitors played a significant protective effect in mild steel corrosion in 1 mol/L HCl. The relationship between the inhibition properties and molecular structure had been discussed by quantum chemistry calculation. All the experimental results concluded that both amoxicillin and ceftriaxone acted as good corrosion inhibitors and their inhibition efficiency was in the order of ceftriaxone > amoxicillin.