Comparative behavior study of steel corrosion inhibition kinetics by three phosphate inhibitors with mass loss measurements

Kinetic study of steel corrosion inhibition using three inhibitors based on phosphate (sodium phosphate Na3PO4, potassium monohydrogenphosphate K2HPO4 and, sodium monofluorophosphate Na2PO3F) was investigated in synthetic mediums of concrete pores solutions contaminated with chlorides at different times up to 60 days by gravimetric measurements. The evolution of inhibition efficiencies for these three inhibitors showed a slightly decrease over time and tend to stabilize between 30 and 45 days. The pH at initial time and final time was also recorded; it reveals that pH decreases slowly comparing with initial time, also comparing with pH of Blank solutions. The effect of temperature was studied for these three inhibitors in order to determine the influence of this parameter on the corrosion inhibition kinetics; it shows that increasing of temperature reduces inhibitors effectiveness. Moreover, thermodynamic studies indicate that adsorption of inhibitor molecules is spontaneous and leads to physical adsorption through Langmuir isotherm model.