Green Synthesis of Novel Schiff Bases as Eco‐friendly Corrosion Inhibitors for Mild Steel in Hydrochloric Acid

Abstract

Two novel Schiff bases, (E)-N-(4-hydroxy-3-methoxybenzylidene)lysine (1) and (E)-N-(4-hydroxy-3-methoxybenzylidene) arginine (2) were synthesized by using natural products of amino acid and vanilline, and their inhibitive effect on the corrosion of mild steel in 0.5 mol⋅L À 1 HCl solution was evaluated by various experimental methods such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves, scanning electron microscope (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Moreover, quantum chemical calculations and molecular dynamics simulations were used to theoretically explore the internal relation between inhibitory efficiency and molecular structure. The results of EIS show the polarization resistance of mild steel is increased from 6.592 Ω⋅cm 2 to 36.46 Ω⋅cm 2 and 74.78 Ω⋅cm 2 in the presence of 1 and 2, respectively. Tafel curves indicate HMBL and HMBA act as good inhibitors for iron corrosion in hydrochloric acid and that 2 has the better performance than 1. XPS analysis confirms the adsorption of inhibitor molecules on iron surface by forming inhibitor-Fe complex, which is well fitted by Langmuir model.[a] Dr.

Synthesis, characterizations, crystal structure, inhibition effects and theoretical study of novel Schiff base on the corrosion of carbon steel in 1 M HCl

“…It is clearly proved in the literature that molecules with high dipole moments and greater than the dipole moment of H 2 O (1.88 Debye), are more reactive [65]. In our study, the high value of the dipole moment of L is 5.25 Debye in the gas phase and 9.40 Debye in the aqueous phase confirm the high reactivity, so the absorption of inhibitory molecules on the metal surface may becomes strong [47].…”

“…The calculated ΔG°a ds value varies between -31.69 and -35.89 kJ mol -1 implying that the adsorption behavior of the inhibitor L involves both physical and chemical interactions [47,48]. ΔG°a ds value being closer to -40 kJ mol -1 , therefore chemical adsorption is more important than physical adsorption.…”

Recent Advances on the Corrosion Inhibition Behavior of Schiff base Compounds on Mild Steel in Acidic Media

“…In terms of corrosion investigations, the formation of a metal complex between inhibitor molecules as electron donors and metal surface atoms as electron acceptors through unoccupied d‐orbital of iron atoms was suggested, [74] which this feature can be boosted by an increase of coordination sites; thereby improving corrosion inhibition possibly [16a,c,75] . To improve the adsorption power of the organic inhibitors, their chemical structures can be modified by changes in the number, position, and nature of heteroatoms, rings, and substitute groups; thus, this helps the stability of the adsorbed film on the metal substrate [76] …”

Green Organic Inhibitors for Corrosion Protection

“…Kegui Zhang and coworkers [17] synthesized two novel Schiff bases from renewable sources such as vanilline and amino acids -L-Lysine and L-Arginine by a green method (Fig. 3).…”