Considerations on the repassivation of corroded reinforced concrete structures

An analysis is made of the responses of clean and precorroded steel electro des in Ca(OH)(2) saturated solutions and in cement mortar, using gravimetri c, metallographic and electrochemical techniques, essentially polarisation resistance measurements. The paper aims to answer some important questions about the corrosion of reinforced concrete structures (RCS) which, though s eemingly elementary, continue to arouse controversy in scientific, technica l and economic circles, such as the following: What corrosion rates are dan gerous in RCS? What concrete resistivities guarantee sufficient durability of RCS? Is it possible to detain corrosion once it has begun? Can corroded RCS be repassivated? Are electrochemical RCS rehabilitation methods efficie nt, and if so, when? The results obtained indicate that electrochemical chl oride removal and realkalisation cannot repassivate heavily corroded steel surfaces, however they can be effective methods to prevent corrosion provid ed they are used before the transition from the passive state to the active one occurs. If applied to late, are useless for this purpose.