Corrosion Performance of Stainless Steel Clad Rebar in Simulated Pore Water and Concrete

The corrosion performance of stainless steel clad reinforcing bar (SCR) was investigated. Corrosion potential of SCR in various alkaline media as a function of time was measured periodically and corrosion rates were estimated using Electrochemical Impedance Spectroscopy (EIS). At room temperature, SCR without cladding breaks was free of corrosion for up to one year in all the testing conditions: saturated Ca(OH)2 solutions (SCS, pH ~12.6), simulated pore solution (SPS, pH ~13.6), simulated carbonated concrete pore solution (CPS, pH <10) (each with 15 wt% chloride by the end of test), and concrete with chloride up to 8% chloride by weight of cement. SCR without cladding breaks also remained passive at 40 C in SCS with 15% chloride and in concrete with 8% chloride. SCR with a 1 mm hole corroded actively in SCS with 15% chloride. The results suggest that carbon steel exposed by the small hole was corroding actively at a high local rate. A model for SCR with a single cladding break at one cut-end in concrete was modeled using a finite differences approach. Calculations indicated that the resistivity of concrete and size of cladding breaks were critical parameters in establishing the rate of corrosion, and that corrosion of SCR with sub-millimeter breaks in high quality concrete would cause concrete cracking only after long service times.