Inhibiting steel corrosion in heavily carbonated solution simulating concrete in marine environments

TOLOSA E.; M. A. FRONTINI; L. YOHAI; VAZQUEZ M.; M. B. VALCARCE

JOURNAL OF THE ELECTROCHEMICAL SOCIETY

ELECTROCHEMICAL SOC INC

Año: 2023

0013-4651

The effect of biphosphate ions as potential inhibiting agents for construction steel is analyzed in heavily carbonated solutions(HCS) simulating concrete where [HCO3−] + [CO3=]) = 0.315 mol l−1. Three conditions are analyzed, always keeping pH = 9: 1)a highly carbonated pore simulating solution (HCS); 2) HCS contaminated with NaCl 0.1 mol l−1; and 3) HCS contaminated withNaCl 0.1 mol l−1 and incorporating biphosphate ions as inhibiting agent. In this last condition, three inhibitor dosages are tested,where the ratios [HPO42−]/[Cl−] are 0.2, 0.6, and 1. The results are compared to previous studies in solutions containing ten timesless carbonate content. Several electrochemical and surface techniques are used to correlate inhibiting efficiency of biphosphateions to dosage. The incorporation of biphosphate ions as inhibitors improves the resistance against localized corrosion. Thepassivating film is composed of a mixture of phosphates and oxides, mainly Fe(III) species. The inhibition efficiency is sensible tothe content of biphosphate and carbonate ions in solution. The optimal dosage of Na2HPO4 is 0.06 mol l−1, where the inhibitionefficiency evaluated over 6 weeks is higher than 99%. The benefit of using Na2HPO4 in proper concentrations as an efficientcorrosion inhibitor is demonstrated for the experimental conditions under study