Cephradine as corrosion inhibitor for copper in 0.9% NaCl solution

The effect of (6R,7R)-7-[[(2R)-2-amino-2-cyclohexa-1,4-dien-1-ylacetyl]amino]-3-methyl-8-oxo-5-thia-1-azobicyclo[4.2.0]oct-2-ene-2-carboxylic acid (cephradine) on corrosion behavior of copper in 0.9% NaCl solution was investigated. The electrochemical methods including the open circuit potential measurements, potentiodynamic polarization and electrochemical impedance spectroscopy measurements, scanning electron microscopy with energy dispersive X-ray spectroscopy and quantum chemical calculations were used for this investigation. According to the results obtained by potentiodynamic polarization, cephradine acts as mixed type inhibitor. Also, the results obtained by electrochemical impedance spectroscopy indicate that cephradine provides good copper protection in 0.9% NaCl solution. The inhibition efficiency of cephradine increases with increasing its concentration. The scanning electron microscopy with energy dispersive X-ray spectroscopy confirms that a protective layer is formed on the copper surface due to the adsorption of cephradine on the active sites on the copper surface. Adsorption of cephradine in 0.9% NaCl solution follows the Langmuir adsorption isotherm. Quantum chemical calculations are in agreement with results obtained by electrochemical measurements. (C) 2018 Published by Elsevier B.V.