Cathodic Behavior of ~9% Cr Steel Reinforcement in Concrete

An important factor in predictive modeling of reinforcement corrosion is how much cathodic reaction it can support, since strong cathodic action shortens the corrosion propagation stage. This is of interest for alternative Cr alloy rebars materials, which not only better resist corrosion initiation but also tend to be weaker cathodes than plain steel. Cathodic strength was evaluated for ~9% Cr rebar approaching the ASTM A1035 specification.  Rebars of ~9%Cr and conventional plain steel were tested for several months in concrete by cyclic cathodic potentiodynamic polarization, both in the as-received condition with mill scale, and sand blasted.  Initial results suggest that as-received ~9% Cr rebar was a much weaker cathode, by a factor of ~5, than plain steel rebar. In the sand blasted condition the difference was less pronounced, indicating that surface scale plays a key role. Estimations of the potential beneficial impact of variations of cathodic strength on service life are presented.