Exploratory Assessment of Corrosion Behavior of Stainless Steel Clad Rebar: Part 1— Experimental

Corrosion behavior of stainless steel clad rebar (SCR) was investigated in both model solutions (initial pH: 10, 12.6, and 13.6, respectively, Cl– up to 15%, ~5 M) and concrete (up to 8% admixed Cl– by weight of cement). The unblemished acid-pickled Type 316L (UNS S31603) stainless steel (SS) lateral surface of SCR (in both solutions and concrete) was found to have high corrosion resistance comparable to that observed for solid SS bars in concrete. Limited evaluations conducted at 40°C showed some tendency for incipient corrosion of the sound lateral SCR surface under the most severe test conditions. Cut-end rebar termination by a proprietary SS cap attached with organic adhesive or a weld overlay showed no failures in limited yearlong experiments at room temperature. However, there was one cap adhesive failure when tested at 40°C, underscoring the need for extended evaluation of cut-end terminations. SCR specimens with small cladding breaks (1-mm or 4-mm ϕ drilled holes), as expected, developed corrosion of the exposed carbon steel (CS). However, corrosion of the CS was delayed or did not take place in some cases, possibly as a result of the stochastic nature of corrosion initiation and the small area of CS exposed at the breaks. Cladding separation at the CS/SS interface (delamination), likely aggravated by expansive corrosion product accumulation, was observed in some instances around the corroding CS at the break. There was indication that corrosion product accumulation at some of the breaks mitigated the corrosion progression.