Adsorption and corrosion inhibition of amphiphilic compounds on steel pipeline grade API 5L X52 in sulphuric acid 1 M

The effect of seven amphiphilic compounds, on steel API 5L X52 corrosion in sulphuric acid 1 M solution was studied by potentiodynamic polarization curves, and electrochemical impedance spectroscopy (EIS). Potentiodynamic polarization curves indicated that these compounds acted mainly as cathodic type inhibitors. The EIS spectrums showed that the mechanism of corrosion inhibition is mainly a faradic process, the spectra were fitted with one electrical equivalent circuit (EEC) using a constant phase element (CPE). Double layer capacitance associated with CPE was also obtained. Langmuir, Temkin, and Henry adsorption isotherm described the experimental findings. This information suggested that organic molecules were adsorbed on active sites on metal surface avoiding contact of corrosive media with steel surface, having adsorbate molecules low molecular interaction between them even with the presence of more amphiphilic molecules on the steel surface as concentration got higher values.