Expired azithromycin and cephalexin as corrosion inhibitors for aluminum in saline-acidic solution

The research aims to study the corrosion of aluminum (5083AA) in saline-acidic solution (pH=1) in the absence and presence of 100 to 200 ppm of azithromycin (AZM) and cephalexin (CFX) as corrosion inhibitors at a temperature range of 293 to 308 K. The electrochemical polarization method was used to estimate the corrosion potential, corrosion current density, and Tafel slopes. The results show that the inhibition mechanism was due to the adsorption of azithromycin and cephalexin molecules on the surface of aluminum. The inhibitor performance, or inhibition efficiency percentage (%η), was increased with an increase in inhibitor concentration, and it was decreased with the temperature increases. Maximum corrosion inhibition efficiency was 75 % and 72 % for cephalexin and azithromycin at 200 ppm and 293 K, respectively. Polarization measurements showed that cephalexin and azithromycin have been physically adsorbed on the aluminum surface as mixed-type inhibitors and obeyed the Langmuir adsorption isotherm. Thermodynamic and kinetic parameters, such as activation energy, enthalpy of adsorption, and entropy of adsorption, were calculated to elaborate the mechanism of corrosion inhibition.