Corrosion Inhibition of API 5L X60 Steel in Acid Medium: Theoretical and Experimental Approaches

The properties of the ionic liquid (IL) trimethyldodecyl(tetradecyl)ammonium diphenyl-2,2'-dicarboxylate (C_12-14TC₁AmD) as a corrosion inhibitor (CI) of API 5L X60 steel in 1 M H₂SO₄ were studied at 298, 308, and 318 K. The inhibition efficiency (IE, %) was established by means of electrochemical techniques. The analysis confirmed that C_12-14TC₁AmD inhibited the corrosion process with a maximal IE of 90 ± 6% at 150 ppm. The inhibitor chemical configuration was a key factor in its physical (cation) and chemical (anion) adsorption on the steel surface, forming a protective film; due to the foregoing, the IL was classified as a mixed-type CI. Finally, the X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of IL on the metal surface, and scanning electron microscopy (SEM) evidenced less surface damage.