The Synergistic Effect of Acetanilide and Para Hydroxy Acetanilide for Corrosion Protection of Carbon Steel in a NaCl Medium

The acetanilide AC and the para-hydroxy acetanilide PHA are used in this work as corrosion inhibitors of the carbon steel (UNS G10260) in a solution of NaCl 3%. In this research using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The set of the results shows that the studied compounds have varied inhibition efficiencies and the adsorption of composed on the surface the metal is made according to the isotherm of Langmuir. The compound PHA presented the best power of inhibition to a concentration of 60ppm (R˃89%). The results showed that the adsorption of AC and PHA is connected to the concentration of every inhibitor and strongly influenced by the temperature. The study thermodynamics showed that the process of adsorption is spontaneous (the negative free energy), physical type of the PHA and chemical for the AC. The effect of synergy between both inhibitors (AC+PHA) was also examined in the chlorinated environment. With different mixtures concentrations of both inhibitors, an efficiency maximum attaint 99.15% for 20 ppm of AC+60 ppm. Cooperative adsorption for all the mixtures.