Natural synephrine as an eco-friendly corrosion inhibitor for steel in acidic conditions: experimental and theoretical study
Le résumé fourni par la source
This study presents an anti-corrosion strategy for carbon steel in 1 M HCl using synephrine, a phytochemical derived from Citrus aurantium. Synephrine was extensively analyzed using FTIR and NMR techniques, while its anti-corrosion properties were examined through electrochemical and computational studies (conceptual density functional theory (DFT) and molecular dynamics simulations (MDS)). EIS revealed a significant, concentration-dependent increase in the charge transfer resistance, which is attributed to the formation of a protective adsorbed layer. Consequently, the total resistance increased consistently with synephrine concentration, with the maximum corrosion inhibition efficiency reaching 84% at 2.0 g/L synephrine. Mixed-type anti-corrosion properties were demonstrated by the Tafel plots, showing a balanced impact on both the anodic and cathodic branches, which is attributed to the suppression of steel dissolution and the organized protective influence of both the hydrogen evolution process and the oxidation of ions that are free of oxide. Comparatively, time-dependent EIS experiments revealed that the inhibited system exhibited significantly higher impedance values than the uninhibited system, suggesting that the adsorption of synephrine onto the surface of steel provided an additional barrier against the aggressive species from the solution, thereby prolonging the corrosion resistance of the metal. SEM analysis validated the adsorption of synephrine and its corrosion protection effects on the surface of the test coupons, whereas DFT and MDS revealed strong adsorption of synephrine on Fe (110), with an interaction energy of −85.72 ± 4.2 kcal/mol, facilitated by heteroatoms and π-electrons. Overall, the sustainable characteristics of synephrine make it a compelling candidate for further investigation.
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