Corrosion inhibition of Carbon Steel using a new morpholine-based ligand during acid pickling: Experimental and theoretical studies

Abstract

Here, a novel, relatively inexpensive Schiff base ligand (HL) has been studied as a corrosion inhibitor for the protection of steel in acidic solution. Different concentrations (0–25 ppm) of HL were added to the test solution and corrosion rate of steel and inhibition efficiency were determined. The obtained results indicated that HL is an efficient steel inhibitor in HCl solution and exhibits the maximum inhibition efficiency of 87.3 % at low concentration of 25 ppm. The EIS measurements revealed that polarization resistance increased from 319 Ωcm2 to 2893 Ωcm2, when the HL concentrations increased from 0 ppm to 25 ppm in HCl solution. Electrochemical experiments revealed that HL acted as a mixed type inhibitor, slowing both cathodic and anodic processes through adsorption which obeyed the Langmuir isotherm. The increase in inhibition efficiency up to 94.6 % with increase in immersion time up to 24 h was observed. Corrosion morphologies were observed by SEM to verify qualitatively the results obtained by electrochemical measurements. Quantum chemical calculations showed the preferred sites through which the molecules can interact with steel surface.