Electrochemical and XPS Studies of Benzalkonium Chloride for Carbon Steel Protection in Hydrochloric Acid
The efficiency of benzalkonium chloride (BKC) to inhibit the corrosion of carbon steel API 5L in 1 M HCl has been studied by potentiodynamic polarization method and X-ray photoelectron spectroscopy (XPS). Potentiodynamic polarization indicated that BKC is able to retard the corrosion reaction of carbon steel and its corrosion rate decreased with the increasing of BKC concentration up to optimum concentration 7.5 mM. Adsorption and thermodynamic studies indicated that BKC molecules were capable of adsorbing onto carbon steel surface by following Langmuir adsorption isotherm model and their Gibbs free energy obtained at 25, 40, 55 and 70°C were -29.15, -31.67, -37.46 and -35.76 kJ/mol, respectively. Thermodynamically point of view shown that adsorption mechanism of BKC onto carbon steel occurred via both physisorption and chemisorption process. While, adsorption mechanism establish by XPS analysis indicated that BKC was dominantly inhibit the carbon steel via physisorption process. As a conclusion, both potentiodynamic polarization method and XPS suggested that BKC is able to adsorb onto carbon steel and protect the surface from actively react with HCl.