Three novel morpholinium-cationic surfactants (coded: DCSM-8, DCSM-10, and DCSM-12) with
chemical structure confirmed via FT-IR, HNMR, and mass analysis were applied for carbon steel
(CS) corrosion control in acidic 4 M HCl solution. The investigated compounds decreased water
surface tension (72 mN.m-1) to 19.85 mN.m-1 after the addition of DCSM-12. The surfactants
mitigation performance was assessed via weight loss (WL), potentiodynamic polarization (PDP) and
electrochemical impedance spectroscopy (EIS). The synthesized surfactants protected CS efficiently
with higher inhibition efficiencies up to 97.029% at 1 × 10–3 M for DCSM-12 using PDP which also
indicated that, the prepared surfactants inhibited both CS anodic and cathodic sites with cathodic
dominant. EIS data showed higher CS resistance from 35.24 Ω.cm2 to 1245.54 Ω.cm2 after addition of
1 × 10–3 M for DCSM-12 with mitigation potency 97.17% which can be attributed to their adsorption
process over CS surface forming a protective film layer that followed Langmuir adsorption isotherm
reflecting the chemical adsorption affinity of the prepared mitigators with higher adsorption energy
(ΔG*ads) values (> -40 kJ.mol-1). Also, the protection effect of the prepared inhibitor (DCSM-12) was
confirmed using SEM (scanning electron microscopy) and EDX (energy-dispersive X-ray) showing
improvement in CS surface morphology. The reactivity of the prepared surfactants and their mitigation
role in CS deterioration were confirmed theoretically using DFT (density functional theory) and MCs
(Monte Carlo simulations). |
