Synthesis, characterization and evaluation of some anionic surfactants with phosphate group as a biodegradable corrosion inhibitor for carbon steel in acidic solution

Novel anionic surfactants with phosphate group were synthesized and characterized by using FTIR and 1H NMR spectroscopic analyses. The critical micelle concentration (CMC) and degree of dissociation of counter-ions were determined and discussed from conductivity measurements. The biodegradability of these surfactants was determined and discussed. Their corrosion inhibition effect on the carbon steel (CS) in 0.5 M H2SO4 solution has been evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and weight loss methods. The inhibition efficiency increases with increasing the inhibitor concentration but decreases with the temperature increasing. The adsorption of inhibitors on the carbon steel surface obeys the Langmuir adsorption isotherm. Polarization curves show that the synthesized inhibitors are mixed-type inhibitors. Thermodynamic parameters of adsorption and kinetic were obtained from weight loss at different temperatures (25-60 °C).