Corrosion behavior of stainless steel clad rebar

The chloride-induced corrosion of regular carbon steel (CS) rebar has caused severe infrastructure durability problems at tremendous cost. Stainless steel (SS) rebars have high corrosion resistance in concrete environment but at much higher cost than CS rebar. Stainless steel clad rebar (SCR), consisting of a stainless steel (SS) clad and a CS core, could be a promising economic alternative of SS rebar. Corrosion behavior of SCR was investigated in this study.; SCR specimens with mortar caps or protected with welding overlay or SS cap were tested in model solutions (up to 15% Cl−) and concrete (up to 8% Cl− by weight of cement) using open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) techniques. The chloride threshold C_T of SCR was estimated to be between 5 and 8% by weight of cement which is in agreement with the literature. The effects of pH and temperature were found to be very small. The observed corrosion of SS surface of SCR under a SS cap (likely due to SS cap disbondment), however, brings up an important caution against over optimistic projection of SCR to long service time.; SCR specimens with a 1 mm &phis; hole (exposing ∼0.008 cm 2 CS) were found to corrode actively in SCS with 15% Cl− . However, specimens tested in saturated Ca(OH)₂ solution (SCS) with chloride increased stepwise up to 5.5% showed high corrosion resistance which was attributed to the stochastic nature of pitting corrosion. Corrosion of SCR in concrete with 8% Cl− was either minor or delayed. Metallographic analysis showed that some SCR specimens experienced cladding delamination at CS/SS interface which was ascribed to corrosion activity.; The cathodic behaviors of type 316LN SS rebar and SCR were tested extensively in model solutions and concrete using cyclic polarization (CYP) technique. The cathodic efficiency of sandblasted or as-received SS surfaces was found to be much smaller than that of CS rebar. However, it increased dramatically when the SS had high temperature oxide scale.; Corrosion of SCR with defects was investigated using 1-D and 2-D models. Calculations indicated that corrosion of SCR is mainly controlled by the concrete quality and the size of cladding breaks. Corrosion of SCR with widely spaced sub-millimeter breaks could be tolerable in concrete which retains high quality. The two models were found to have comparable output.