The inhibitive effect by dirithromycin, an antibacterial drug, on the corrosion of zinc has been investigated using weight loss method. The results obtained indicate that clindamycin inhibits zinc corrosion in tetraoxosulphate(VI) acid (0.01 to 0.04 M) media. The inhibition efficiency increased with increasing inhibitor’s concentration. Kinetic, thermodynamic and adsorption parameters were determined and discussed. The uninhibited corrosion of zinc followed first order kinetics; while the presence of dirithromycin increased the enthalpy of activation, Δ H‡ and therefore made corrosion less probable. The calculated Δ G‡ values for the corrosion processes were positive, but increased in the presence of dirithromycin, suggesting that the activated complex was rather unstable. The adsorption of dirithromycin on zinc surface was exothermic, spontaneous and was best described by Langmuir adsorption isotherm. The calculated values of activation energies and free energies of adsorption indicate that the adsorption process supports the mechanism of physical absorption.
Adsorption, Corrosion kinetics, Inhibition, Dirithromycin, Inhibition Efficiency, Activation thermodynamics