cathodic protection for reinforced concrete structures pdf
How steel corrodes in concrete is of significant importance when trying to understand the likely mechanisms and possible rates. If a clean-surfaced, grit-blasted, rebar is put in a saline, pH-neutral
solution, then there will be a rapid browning over the whole surface area. A bright yellowish brown oxide will form within minutes and gradually become darker as the exposure time increases. This
is commonly referred to as microcell corrosion, as it is appearing evenly over the whole surface of the rebar. As the exposure time increases, the rate of corrosion reduces, as the oxide layer provides
a barrier to ionic, atomic and gaseous transport.
In reinforced concrete structures, when the contaminated concrete cover is removed after many years, the corrosion process is not so simple. There can be areas where corrosion appears to be
general with uniform section loss (refer to Figure 1.1). This tends to be in areas with lower cover depth and relatively dry carbonated concrete.