Chloride Threshold Dependence on Potential in Reinforced Mortar

Abstract

Abstract Additional assessment of the chloride threshold dependence on steel potential is presented to supplement the limited set of available data. Cylindrical mortar specimens with an embedded steel rebar were exposed to NaCl saturated solution under potentiostatic control at open circuit potential and -200, -400 and -600 mV vs. saturated calomel electrode (SCE). Once corrosion started, the specimens were demolished and the chloride content at the rebar surface was determined and reported as the chloride threshold (CT) for that condition. The present results tend to agree with those of previous investigators showing that negative polarization of several hundred mV may be needed to attain an increase in corrosion initiation threshold of about one order of magnitude. An updated survey of the literature is consistent with the lower bound of that beneficial effect being approximately described by a threshold value in the order of 0.5% by weight of cement at E=-100 mV (SCE), with a negative slope provisionally in the order of ~550 mV per decade of chloride content.