Synergetic effect of two inhibitors for enhanced corrosion protection on the reinforcing steel in the chloride-contaminated carbonated solutions

The synergetic inhibiting effect of benzotriazole (BTA) and Na2HPO4 for the corrosion of reinforcing steel in the chloride-contaminated carbonated solutions was preliminarily investigated by electrochemical measurements, as well as X-ray photoelectron spectroscopy and scanning electron microscopy/energy dispersive X-ray techniques. Results show that a mixture of BTA and Na2HPO4 acts as an anodic inhibitor. An optimum enhanced inhibition efficiency was obtained for a mixture of 0.05 M BTA and 0.05 M Na2HPO4. The synergistic inhibiting mechanism for steel was proposed, which was by forming a protec-tive film consisting of Fe-n(BTA)(m) complex and iron phosphates, as well as hydrogen bonding between them on the steel surface. On the contrary, a mixture of unequal amount of BTA and Na2HPO4 showed an antagonistic effect on corrosion inhibition resulting from the competition between the phosphate ions and BTA- on the steel surface. (C) 2021 Published by Elsevier Ltd.