Three piperazine compounds as corrosion inhibitors for copper in 0.5 M sulfuric acid medium

Abstract

BackgroundSearching for and developing green corrosion-resisting drugs plays an significant role in protecting Cu during its pickling treatment. The toxicities and inhibitive performances are closely correlated with their molecular formulas. MethodsTherefore, Amoxapine, Loxapine and Clozapine, all of which belong to piperazines, were assessed as inhibitive agents to protect Cu from corrosion in 0.5 M H2SO4 via electrochemical measurements, surface morphologies and theoretical calculations. According to the electrochemical results, the anti-corrosion efficiencies of AP, LP and CP reached their maximums at 5 mM, namely 94.0༅, 95.2༅ and 96.6༅, respectively. They were all proved to be cathodic-type corrosion inhibitors. The morphology analysis implied the shaping of protective films on Cu surfaces. Moreover, the absorption of AP, LP and CP on Cu surfaces deferred to the Langmuir isotherm model, confirming the analysis of Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Theoretical calculations revealed their adsorption models and anti-corrosive mechanisms. Significant FindingsBoth experiment and calculation manifested favourable corrosion-proof properties of the three researched drugs. Further analysis also proved the enhanced inhibitive effect of methyl that connected with benzene ring owing to its conjugative effect. Furthermore, N atom possessed higher electronegativity and accordingly stronger electron-donating ability compared to O atom. The corrosion-resisting efficiency of Clozapine was 96.6%, being higher than that of Loxapine which was 95.2%.