An amino‐based protic ionic liquid as a corrosion inhibitor of mild steel in aqueous chloride solutions

• Published in: Materials and corrosion Vol. 71; no. 7; pp. 1175 - 1193
• Main Authors: Schmitzhaus, Tobias Eduardo, Ortega Vega, Maria R., Schroeder, Roberto, Muller, Iduvirges Lourdes, Mattedi, Silvana, Malfatti, Célia de Fraga
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-07-2020
• Subjects: Adsorption; carbon steel; Chemical composition; Chlorides; Corrosion; corrosion inhibition; Corrosion inhibitors; Corrosion mechanisms; Electrochemical analysis; electrochemical techniques; Ionic liquids; Ions; Low carbon steels; Morphology; protic ionic liquid; Raman spectroscopy; Spectrum analysis; surface analysis
• ISSN: 0947-5117; 1521-4176
• DOI: 10.1002/maco.201911347

Protic ionic liquids (PILs) have shown to be promising substances as corrosion inhibitors (CIs). In line with this, the aim of this study is to study the performance and propose the corrosion inhibition mechanism of N‐methyl‐2‐hydroxyethylamine (M‐2HEAOL) and bis‐2‐hidroxyethylamine (B‐HEAOL) oleate, for mild steel, in a neutral chloride solution. Electrochemical characterization was conducted under static and hydrodynamic conditions, and it was revealed that M‐2HEAOL and B‐HEAOL worked as mixed‐type CIs with more interference on the anodic reaction. Inhibition efficiency depended on the concentration reaching 97% of inhibition efficiency in 5 mmol/L concentration. Scanning electron microscopy, optical interferometry, Raman spectroscopy, and Fourier‐transform infrared spectroscopy are used to elicit the chemical composition of the surface film and corrosion morphology of steel in the presence of CIs, the adsorption processes of which involved physical and chemical adsorption between metal and different parts of ionic liquids. The results allowed the proposition of a corrosion inhibition mechanism.
Two oleate‐based amino protic ionic liquids were tested as corrosion inhibitors for mild steel in sodium chloride electrolyte. The results show that both anodic and cathodic reactions are affected but the effect on the anodic one is much more prominent. Inhibition efficiencies reached 95–98%. The ionic liquids formed a protective layer on steel by a mixture of physisorption and chemisorption.