Investigation of some expired antibiotic drugs: Effect on the corrosion inhibition of mild steel in 0.1 M HCl medium via experimental and molecular dynamics simulation

Abstract

Three expired antibiotic drugs namely, ampiclox, ciprofloxacin, and ampicillin were studied at low concentrations on the corrosion inhibition of mild steel (MS) in 0.1 M HCl medium using weight loss and scanning electron microscopy (SEM) techniques. Subsequently, the molecular structures of the antibiotic inhibitors were subjected to molecular dynamic (MD) simulation using Material Studio 8.0 software to have insight into their dynamic binding energy onto the Fe (110) surface in an acidic medium. The results showed that the weight loss and corrosion rate decrease with an increase in the inhibitor concentration, while the inhibition efficiency (%) and surface coverage increase with the increase in the inhibitor concentration respectively. The maximum inhibition efficiency of 97.72 % was attained at 0.009M concentration for ciprofloxacin followed by ampiclox and ampicillin. The SEM analysis of the MS with the expired ciprofloxacin (0.009 M) revealed a soother surface through the formation of a protective film that prevented the corrosion attack which confirms the highest inhibition efficiency. The MD simulation showed that the ciprofloxacin has the highest binding energy of -474.582 kcal/mol, followed by -248.448 kcal/mol for ampicillin and -234.955 kcal/mol for ampiclox respectively. Hence, the ciprofloxacin with the more negative magnitude of the binding energy was predicted to exhibit stronger chemisorption interaction onto the Fe (110) metal surface when compared with ampicillin and ampiclox. The findings in this research reveal good agreement between the experimental and theoretical results in studying the corrosion inhibition of the studied antibiotic drugs.

Keywords

• corrosion
• mild steel
• molecular dynamics
• binding energy
• antibiotic drug