Exploratory Assessment of Corrosion Behavior of Stainless Steel Clad Rebar: Part 2—Modeling of Galvanic Corrosion at Cladding Breaks

The galvanic corrosion of exposed carbon steel at stainless steel clad rebar (SCR) breaks was investigated computationally with both spatially detailed (2-D finite difference) and broadly scaled (1-D transmission line) models at cladding break/rebar-size scale, and at the structural-size scale. The two models were found to have comparable outputs in the cases of interest. Computation indicated that the corrosion rate of exposed carbon steel in SCR depended strongly on the resistivity of concrete and clad break size. A simple empirical equation was obtained describing the relation between nominal corrosion rate and the two parameters. The projected corrosion rates, however, were only modestly sensitive to the choice of the anodic exchange current density (i_oa) of the corroding carbon steel and the cathodic exchange current density (i_oc) of the surrounding passive stainless steel. The calculations suggested that widely spaced cladding breaks of sub-millimeter size could be tolerable in a concrete structure with sufficient concrete cover (e.g., >7.5 cm) and high resistivity (e.g., ≥30 kΩ·cm). However, scenarios with reduced local resistivity and increased size of an assumed corrosion product-contaminated concrete zone surrounding the break suggested possible increases in corrosion severity that merit further investigation.