Experimental Study and Quantum Calculations for Spiramycin and Isosorbide Dinitrate as Corrosion Inhibitors

Abstract

The investigation of the efficiency of two expired drugs, including Spiramycin and Isosorbide dinitrate, was done as corrosion inhibitors for aluminum in 0.1M HCl medium using the electrochemical method by Potentiostst at four temperatures (293, 303, 313, and 323 K) and 200 ppm as constant concentration for each drug. The results showed that these drugs gave good efficiencies equal to 98.836% and 94.285 % for Spiramycin and Isosorbide dinitrate at 293 K, respectively, by adsorption process on the metallic surface. They act as mixed-type inhibitors due to shifting corrosion potential either to active or noble direction. The corrosion data were measured and debated, where the corrosion current density was decreased after adding expired drugs to the corrosive medium due to inhibiting the cathodic and anodic reactions (i.e., the dissolution and reduction reactions). Using SEM exam, the inhibited surface of specimens was characterized to confirm the coverage of the surface by drug molecules. The adsorbed layer by Spiramycin was better than that by Isosorbide dinitrate. Also, the Fourier transform infrared spectra were used to limit the active site attracted to the surface by adsorption that confirmed the attraction by hydroxyl and nitro groups, as illustrated by the mechanism of inhibition. In addition, the antibacterial activity of the inhibitors against some types of bacteria was tested to confirm the formation of an inhibition zone against bacteria. The quantum chemical parameters exhibited a good correlation with the inhibition efficiency.

Keywords

• expired drugs
• corrosion inhibition
• aluminum
• tafel plot