Steel Activation in Concrete Following Interruption of Long-Term Cathodic Polarization

Abstract

A set of partially immersed reinforced concrete columns with mature corrosion patterns was used to demonstrate that corrosion macrocell currents provided “cathodic prevention” to parts of the steel assembly that remained passive even though it was exposed to high chloride concentrations (up to ~4.7% of the cement weight) by the end of nine years of testing. The potential of that steel increased following macrocell decoupling, and instances of depassivation were observed 15 days to 75 days after decoupling. The results are contrasted with previous observations of potential dependence of the chloride corrosion threshold in concrete, and an approximate functional relationship between the threshold value and the potential is proposed.