Ionic liquids with carboxylic-acid-derived anions evaluated as corrosion inhibitors under dynamic conditions

The present work deals with the evaluation of three novel ionic liquids (ILs): triethylmethyl ammonium laurate (TAL), triethylmethyl ammonium anthranilate (TAA) and triethylmethyl ammonium oleate (TAO). These compounds were evaluated as corrosion inhibitors (CIs) of API 5L X52 steel in 0.5 M H ₂ SO ₄ by means of electrochemical techniques such as polarization resistance (Rp) and Tafel polarization curves. The electrochemical studies were performed at stationary state (N _Re = 0) and transitory regime (N _Re = 3375 and 4500) with concentrations ranging from 10 to 100 ppm. The maximal inhibition efficiencies (IEs) for TAL (78 %) and TAA (73 %) were obtained at 100 ppm and NRe = 4500 whereas for TAO (63 %) the IE was reached at NRe =3375. These results confirmed that the IE is also a function of N _Re . Furthermore, the Langmuir adsorption isotherm indicated that the IL molecules were adsorbed on the metal surface through a physical phenomenon. From the analysis of the results, a mechanism through which the ILs inhibit the corrosion of API 5L X52 steel in 0.5 M H ₂ SO ₄ was proposed.