Corrosion Inhibition Effect of Sodium Tri-Polyphosphate on Reinforcing Steel in Simulated Concrete Pore Solution with Different Phs

The inhibition activity of sodium tri-polyphosphate (STPP) for reinforcing steel in chloride-contaminated alkaline solution with pH ranging from 12.5 to 8.5 was explored via electrochemical measurements and FESEM-EDS surface analysis. Based on the results, STPP, acting as a mixed-type corrosion inhibitor, provided the inhibition efficiencies up to 70% at all studied pHs, thus increasing the corrosion resistance of the steel rebars (at least four times) and reducing the corrosion rate significantly. The DFT and Ab-intio simulations suggested that this inhibition behavior was related to the STPP adsorption via solid chemical bonds between the oxygen heteroatoms of STPP and Fe of the metal surface.