Enhancing the corrosion inhibition behavior of tryptamine hydrochloride using surfactant additives for mild steel in 3.5% NaCl solution

Abstract

The current study deals with the study of the effect of tryptamine hydrochloride (THC) on inhibition of mild steel (MS) in 3.5 % NaCl solution when combined with cationic, i.e., Cetyltrimethylammonium bromide (CTAB), anionic, i.e., Sodium dodecyl sulfate (SDS), and non-ionic, i.e., Triton X-100 (TX-100) surfactants. The inhibition efficiencies of the THC-surfactants system were evaluated using EIS, polarization tests, and weight loss measurements. The results showed a great improvement in the inhibition capacity of THC after the addition of 5 ppm for each surfactant evaluated, in the order THC (65.0 %) < THC+SDS (72.9 %) < THC+CTAB (85.4 %) < THC+TX-100 (95.9 %). The adsorption of THC on the MS surface was found to follow Langmuir adsorption isotherm and acted as a cathodic-type inhibitor in either the absence or presence of surfactants. This shift suggests that the inhibitor primarily suppresses the reduction of oxygen or hydrogen evolution. Additionally, the interaction between the THC and the metal surface was confirmed through FT-IR and UV-vis spectroscopies. The characteristic changes in the FT-IR spectra showed the formation of a protective layer due to the chemical bonding and adsorption behavior of THC on the steel surface. The SEM image supported the results by showing that the surface of the steel treated with THC and surfactants was relatively smoother and more uniform than untreated steel, which suffered severe corrosion damage. The most intact surface morphology with no sign of corrosion was observed in the presence of THC+TX-100, which shows the highest protective effect among all tested surfactant additives.