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The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.

Title:

Testing of Selected Metallic Reinforcing Bars for Extending the Service Life of Concrete Bridges: Testing in Solutions
Authors:
Scully, John R.,
Marks, Christopher A.
Hurley, Michael F.
Year: 2003
VTRC No.: 03-CR11
Abstract: Stainless steel-clad rebar provides an opportunity to significantly increase the Cl- threshold concentration associated with active corrosion initiation compared to plain carbon steel. However, threshold Cl- concentrations for 316L stainless steel-clad rebar are unknown. Moreover, the impact of possible galvanic corrosion between the clad layer and any exposed carbon steel core has not been investigated. The Cl- threshold concentrations for corrosion initiation on clad 316L stainless steel (with a thickness of about 1 mm over a carbon steel core), solid 316LN stainless steel, and plain carbon steel were examined in saturated Ca(OH)2 plus various concentrations of NaCl. The electrochemical properties of "intact" 316L stainless steel-clad rebar were found to be similar to those of solid 316LN stainless steel according to several electrochemical criteria. The Cl- threshold concentrations for corrosion initiation were increased to Cl-/OH- molar ratios as high as 17 to 24 even at high anodic potentials for "intact" 316L-clad and solid 316LN stainless steel, respectively. Thus, active corrosion of "intact" 316L-clad rebar could be delayed for many years due to the high Cl-/OH- molar ratios required at the stainless steel/concrete interface and the slow transport rate of chloride in concrete. In contrast, the threshold chloride concentration for corrosion initiation on carbon steel was low (Cl-/OH- molar ratio < 1.5) at all potentials. Cladding with a physical breech exhibited Cl-/OH- thresholds dominated by the exposed plain carbon steel. Galvanic coupling between exposed plain carbon steel and the stainless steel-cladding accelerated corrosion of the plain carbon steel only at and above the Cl-/OH- ratio necessary for corrosion initiation on carbon steel.