Some Surfactants as Corrosion Inhibitors for Carbon Steel in Acidic Solutions

The corrosion inhibition effect of three different types of surfactants, namely, dodecyl trimethyl ammonium chloride (DTAC), octyl phenol poly (ethylene glycol ether) (TX-100), and dioctyl sodium sulfosuccinate (AOT) have been utilized as corrosion inhibitors for AISI 1037 carbon steel in 0.5 mol L^–1 hydrochloric acid. The inhibition efficiency of the surfactants was studied via chemical and electrochemical techniques. The results proved that the order of protection efficiency is: DTAC > TX-100 > AOT. Also, the data revealed that the inhibition efficiency increases by increasing the concentrations of surfactants and decreases by increasing the temperature of the medium. Polarization curves indicated that the investigated surfactants are mixed-kind inhibitors. The adsorption of these surfactants on the AISI 1037 surface follows the Langmuir adsorption isotherm. The calculated free energy from the Langmuir adsorption isotherm indicated that the investigated surfactants are adsorbed on AISI 1037 via mixed adsorption, i.e. physisorption and chemisorption, in 0.5 mol L^–1 HCl. The results of different tests are in excellent agreement.