Effect of soluble inhibitors on the corrosion behaviour of galvanized steel in fresh concrete

• Published in: Cement and concrete research 2018-05, Vol.107, p.1-10
• Main Authors: Bellezze, T., Timofeeva, D., Giuliani, G., Roventi, G.
• Format: Article
• Language: English
• Subjects: CHROMATES; CHROMIUM; Concrete; Concrete reinforcements; CONCRETES; CORROSION; Corrosion effects; Corrosion inhibitors; Corrosion potential; Diffraction; DISSOLVED GASES; Energy dispersive X ray spectroscopy; Fresh concrete; Galvanized steel; Galvanized steels; Galvanizing; HYDROGEN; Inhibitor; MATERIALS SCIENCE; MOLYBDATES; MONITORING; NITRITES; OXYGEN; PASSIVATION; Passivity; Reinforcing steels; SCANNING ELECTRON MICROSCOPY; SEM; STEELS; X-ray diffraction; X-RAY SPECTROSCOPY
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2018.02.008

The effect of some soluble inhibitors on the passivation time of galvanized steel reinforcements in fresh concrete was studied in order to reduce H2 evolution associated with the active corrosion. The investigation was performed by means of corrosion potential monitoring, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. The obtained results indicate that the passivation of galvanized steel in concrete containing chromates occurs in three steps with different mechanisms and that dissolved oxygen is necessary for the beginning of passivation process. Among the inhibitors studied as alternative to Cr VI, nitrite seem the most promising one, even if it is less effective than chromate. Diethanolamine and molybdate ions do not have significant effect on the passivation time of galvanized steel in fresh concrete. •Metastable passivation of galvanized steel occurs immediately in concrete with Cr VI ≥ 15 ppm.•Stable passivation of galvanized steel in concrete with Cr VI ≥ 6 ppm occurs in three steps.•Nitrite decreases hydrogen evolution by moving corrosion potential to more positive values.•Nitrite favours the formation of a compact layer of CHZ, which leads to a stable passivation.•DEA and MoO42− do not have significant effect on the passivation time of galvanized steel.