Enhanced adsorption of target branched compounds including antibiotic norfloxacin frameworks on mild steel surface for efficient protection: An experimental and molecular modelling study

In this study, an approach was proposed to employ new target branched compounds(TBCs) including multiple antibiotic norfloxacin frameworks for intensified adsorption films to achieve super protection of mild steel in HCl medium. Thus, the TBCs containing bis/tri norfloxacin skeletons were synthesized by multi-step preparation route. In addition, the reference linear compound(RLC) including a single norfloxacin part was also synthesized. The chemical structures of these compounds were confirmed by various means. It was demonstrated that the TBCs could form the tough adsorption films on the surface of mild steel, which could be processed mainly through chemisorption effect. The electrochemical analysis suggested that the TBCs displayed superior corrosion inhibition performance for low carbon steel in1.0 mol·L^(-1) HCl solution over the RLC(RLC, 87.80%;TBC1, 97.63%;TBC2, 98.35%), which was further understood by the molecular modelling. The isotherm adsorption plots were employed to analyze the spontaneous adsorption process of the TBCs on low carbon steel surface, and a prominent chemisorption could be inferred by the standard Gibbs free energy changes of the adsorption.

New branched benign compounds including double antibiotic scaffolds:synthesis,simulation and adsorption for anticorrosion effect on mild steel

In this study,two novel environmental benign double antibiotic norfloxacin or ciprofloxacin scaffolds included branched molecules were prepared by multi-step routes and purified by simple performance,which were used as the target compounds(TCs).Meanwhile,a single norfloxacin or ciprofloxacin skeleton based molecules were synthesized as the reference compounds(RCs).The molecular geometry optimization and material simulation computation revealed that TCs presented smaller HOMOLUMO energy gaps and larger binding energy levels on mild steel surface than RCs.The chemical adsorption of TCs on steel surface was confirmed by X-ray photoelectron spectroscopy,which could be processed by TCs chelation with iron ions.It was shown that TCs could be self-adsorbed on steel surface,which was demonstrated by atomic force microscopy and scanning electron microscopy.The anticorrosion of the studied compounds for mild steel in HCl solution was investigated by electrochemistry analysis.The results suggested that the anticorrosion efficiency could reach 95.86%(TC1)and 97.05%(TC2)at 0.050 mmol·L^(−1) based on electrochemical impedance spectroscopy,which were much better than RCs(RC1,69.23%;RC2,74.16%).The adsorption isotherms of TCs on steel were further fitted,and a deep insight on adsorption was discussed.