Evaluation of the efficiency of 1-ethyl-3-methylimidazolium chloride ionic liquid as corrosion inhibitor for the welded duplex stainless steel in acid environment

In this work, the inhibition performance of the ionic liquid 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) on the corrosion of heat-treated welded joint of duplex stainless steel UNS S31803 in 1 mol L−1 HCl solution at room temperature was investigated using electrochemical measurements, surface analysis, and mechanical characterization. The results obtained from potentiodynamic polarization measurements demonstrated that [EMIm]Cl is a moderate inhibitor for the welded joint in 1 mol L−1 HCl solution and acts as a mixed-type inhibitor with a predominant effect on anodic reactions. The inhibition efficiency increased with the increasing concentration of the inhibitor, reaching a maximum protection of 70% at a concentration of 4 mmol L−1. Surface morphology analysis using confocal microscopy revealed a reduction in surface damage in the presence of the inhibitor, suggesting the formation of a protective film that could inhibit the formation of corrosion products. The adsorption of the ionic liquid on the duplex stainless steel joint followed the Langmuir's isotherm. The thermodynamic parameters indicated that the adsorption of [EMIm]Cl on the duplex stainless steel surface occurred by chemical and physical adsorption process. Therefore, the results indicate that [EMIm]Cl has potential as a sustainable alternative for corrosion protection of welded joints in acidic environments.