Inhibition effect of sparteine isomers with different stereochemical conformations on the corrosion of mild steel in hydrochloric acid solution

Abstract

This work focuses on the study of the adsorption and corrosion inhibition properties of two isomeric compounds, (+)-sparteine and (–)-sparteine, for mild steel (MS) in 1 M HCl. Weight loss experiments, electrochemical measurements, surface morphological analyses and theoretical calculation were applied to investigate and explain the effect of ‘Dextroisomer & Levoisomer’ conformations on the corrosion inhibition performance and mechanism. The experimental results indicated that (+)-sparteine and (–)-sparteine are effective and potential corrosion inhibitors for mild steel in 1 M HCl solution, and their inhibition efficiencies are more than 93% at 1.0 mmol L−1. (–)-sparteine has better corrosion corrosion efficiency than (+)-sparteine, reflecting the importance of molecular stereoscopic configuration on the corrosion inhibition performance. The experimental results confirmed that (–)-sparteine was adsorbed on the surface of metal coupon by sharping a film to prevent metal corrosion. Molecular dynamic (MD) simulations also manifested that (–)-sparteine was absorbed more strongly on the metal surface in a parallel mode than (+)-sparteine. The study provides a trial for the molecular geometry structure and corrosion inhibition property supported by electrochemical experimental and modelling studies.