Sustainable development of an effective anti-corrosion film over the St12-steel surface against seawater attacks using Ce(III) ions/tri-sodium phosphate anions.

One application of organic compounds is to utilize them as corrosion inhibitors in acidic environments to diminish steel corrosion. These inhibitors do not show very good inhibition properties in saline (NaCl) environments. There have been many studies on boosting these inhibitors' performance in such environments (especially Cl containing media). One of the ways that have been proposed is the use of organic and inorganic inhibitors, simultaneously. The synergistic effect of these inhibitors has shown promising results in reducing steel corrosion. In this study, cerium(III) nitrate and tri-sodium phosphate (TSP) was used as organic and inorganic inhibitors to control the corrosion of steel in a 3.5 wt.% NaCl environment. The corrosion measurements were conducted in the 3.5 wt.% NaCl environment by EIS and polarization methods. Surface studies were done by SEM, Raman, GIXRD, and EDS methods. Corrosion studies (EIS and polarization) have revealed that when 500 ppm of Ce(NO) and 500 ppm of TSP are added to the 3.5 wt.% NaCl medium, the highest synergism index (1.27) and inhibition efficiency (73.7%) are achieved. Also, by adding 500Ce-500TPS to the solution, i and R of steel decreased by about 80% and increased approximately 4-fold, respectively. This improvement in the steel performance against corrosion in the presence of an equal ratio of Ce(NO) and TSP is the outcome of the formation of a hydrophobic dense film (consisting of Ce(OH), Ce/Fe-phosphate complexes) on the metal surface. This claim has been proven by SEM/EDS, contact angel, FT-IR, and XRD analysis.