Synergistic inhibition mechanism of phosphate and phytic acid on carbon steel in carbonated concrete pore solutions containing chlorides

Synergistic inhibition performance of trisodium phosphate (TSP) and phytic acid (PA) on chloride-induced corrosion of Q235 carbon steel in carbonated concrete pore solutions was investigated using electrochemical measurements, XPS, AFM and SEM/EDS. At the optimum concentration ratio of TSP and PA, the mixed inhibitor showed an inhibition efficiency of 89.8 % after long-term chloride exposure due to the progressive formation of a protective oxide film with specific bilayer structure on the steel surface, and the corresponding synergistic inhibition mechanism was proposed. However, the excessive content of PA could compete with TSP, thereby leading to an antagonistic effect with reduced inhibition efficiencies. • A mixed inhibitor of TSP and PA shows a synergistic corrosion inhibition on carbon steel. • The mixed inhibitor preferentially adsorbs on carbon steel to prevent pitting corrosion. • An antagonistic effect is highlighted for the mixed inhibitor due to excessive PA content.