Anticorrosive properties of spiramycin for aluminum in acidic medium

Abstract

Aluminum corrosion is a challenge in manufacture processes where this metal and its alloys are exposed to acid solutions. In the presence of a corrosion inhibitor, the damage to the aluminum surface is reduced significantly, meaning that the surface morphology is more protected due to the adsorption of inhibitor molecules onto the aluminum surface. Expired Spiramycin was investigated as a green corrosion inhibitor for pure aluminum in 0.1 M HCl solution at 293, 303 313 and 323 K using the electrochemical method. Three concentrations (100, 150 and 200 ppm) of the drug were used. Corrosion testing showed good inhibition efficiencies (IE%) in 0.1 M HCl medium reaching 98.836% at an inhibitor concentration of 200 ppm and 293 K. The adsorption of Spiramycin on pure aluminum surface followed a Langmuir adsorption isotherm. Corrosion potentials revealed that Spiramycin acts as a mixed type inhibitor. Examination of the inhibited surface by SEM confirmed the adsorption of the drug molecules onto the aluminum surface. Furthermore, EDX analysis was performed. It can be observed that aluminum surface contains a percentage of carbon, hydrogen, and oxygen atoms from the adsorbed drug molecules. AFM indicated that the drug molecules contributed to the formation a protective layer by adsorption on the aluminum surface. A FTIR spectral study showed that the protective deposit consisted of a metal–drug complex. The IR adsorption peaks were attributed to some functional groups of the inhibitor molecules adsorbed on the aluminum surface. Adsorption isotherm calculations indicated that the inhibitor underwent physical adsorption.