Abstract

Following standard experimental (gravimetric measurements, potentiodynamic polarization measurements, electrochemical impedance measurements, spectroscopic measurements, scanning electron microscopy technique) and theoretical (DFT) approach, inhibition effect of L-proline (LPr) and LPr mixed with sodium benzoate (LPr + NaBenz) for mild steel (MS) corrosion in 1M HCl was studied at 30, 40, 50 and 60 °C. The concentration of LPr was varied between 100–600 ppm, whereas that of NaBenz was fixed at 10 ppm. LPr lowered the corrosion rates of MS to a considerable extent. Corrosion mitigating efficacy of LPr is synergistically enhanced on adding NaBenz at all concentrations. Evaluation of polarization parameters suggested that both LPr and LPr + NaBenz act as mixed type inhibitor with more control on cathodic reaction whereas impedance parameters suggested inhibition of metal corrosion by adsorption at the MS/solution interface. Surface microscopic examination of corroded and uncorroded MS coupons supported the protective effect of adsorbed inhibitor layer at the MS surface. Spectroscopic studies are suggestive of the complex formation between inhibitor molecules and the metal. When LPr is combined with NaBenz, the corrosion inhibition rate was improved greatly. Corrosion mitigating efficacy of LPr or LPr mixed with NaBenz obtained by different techniques are in good agreement and correlate well with theoretical quantum chemical descriptors.

Highlights

  • Following standard experimental (gravimetric measurements, potentiodynamic polarization measurements, electrochemical impedance measurements, spectroscopic measurements, scanning electron microscopy technique) and theoretical (DFT) approach, inhibition effect of L-proline (LPr) and LPr mixed with sodium benzoate (LPr + NaBenz) for mild steel (MS) corrosion in 1M HCl was studied at 30, 40, 50 and 60 °C

  • Following standard experimental and theoretical (DFT) approach, inhibition effect of L-proline (LPr) and LPr mixed with sodium benzoate (LPr + NaBenz) for mild steel (MS) corrosion in 1M HCl was studied at 30, 40, 50 and 60 °C

  • Majority of the heterocyclic organic compounds though yielded high inhibition efficacy, their applications is limited by: (i) high cost of production, (ii) toxic by-products often formed during their production leading to environmental concern and (iii) the specificity of action associated with the use of single compound inhibitors

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Summary

Introduction

Following standard experimental (gravimetric measurements, potentiodynamic polarization measurements, electrochemical impedance measurements, spectroscopic measurements, scanning electron microscopy technique) and theoretical (DFT) approach, inhibition effect of L-proline (LPr) and LPr mixed with sodium benzoate (LPr + NaBenz) for mild steel (MS) corrosion in 1M HCl was studied at 30, 40, 50 and 60 °C.

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