The inhibition effects of several inhibitors on rebar in acidified concrete pore solution

The inhibitive effects of several inhibitors for carbon steel in acidified pore solution (pH 8.0) were studied. Sodium molybdate shows good effect to promote passivation at low concentrations (0.013 wt.%), but for sodium tungstate and sodium nitrite higher concentration (0.045 wt.%) is needed to obtain passivation. Sodium phytate only shows minor inhibitive effects at the concentration level of 0.045 wt.%. At higher concentration level (0.045% ⩽ wt.% ⩽ 2%), the inhibitors sodium molybdate, sodium tungstate and sodium nitrite behave well in the acidified pore solution. For sodium phytate, to obtain obvious inhibition the inhibitor concentration must be above 0.5 wt.%. Molybdate and tungstate are present on the steel surface according to Raman spectrum analysis, which supports the adsorption mechanism of the inhibitors.

► Inhibitive effects of Na2WO4 and Na2MoO4 for steel in pH 8 pore solution are studied.
► Na2MoO4 shows good inhibitive effect at low concentration (0.013%).
► Higher concentration (0.045%) is needed for Na2WO4 to inhibit corrosion.
► Sodium phytate also shows inhibitive effect when the concentration is above 0.5%.
► Raman spectrum analysis supports an adsorption mechanism for the two inhibitors.