Chloride-induced corrosion initiation of carbon steel in sulfide-containing cementitious environments
Year: 2026
Type: article
Abstract: The mechanism and consequences of passivation and chloride-induced corrosion initiation of steel in systems with reduced sulfur species (HS − , S n 2− , S 2 O 3 2− , SO 3 2− ), including reinforcement corrosion in concrete, are insufficiently understood to date. In this context, the present study investigated the electrochemical behaviour of carbon steel in synthetic pore solutions simulating ground granulated blast-furnace slag (GGBFS)-containing concrete, with a focus on the combined effects of reduced sulfur species and chloride, under anoxic, oxic and fully oxidised conditions. A three-electrode cell configuration was employed to conduct electrochemical analyses, including measurements of open-circuit potential (OCP), polarisation resistance ( R p ), and electrochemical impedance spectroscopy (EIS) to monitor passive film formation and stability. The critical chloride threshold ( c crit ) for steel corrosion initiation was studied by incremental NaCl additions to the synthetic pore solutions; these solution-based values serve as upper-bound estimates for steel embedded in concrete. In sulfide-containing solutions, steel did not passivate before complete oxidation of the reduced sulfur species, exhibiting OCP values of −550 to −700 mV Ag/AgCl and R p values of 3–50 kΩ·cm 2 . No corrosion initiation occurred up to 4 M chloride in solutions containing ≥ 50 mM HS − , even after oxygen exposure. The behaviour remained independent of pH because reduced sulfur species maintained anoxic conditions at the steel surface, with dissolved oxygen below the detection limit after days of air exposure. Passivation occurred only after complete oxidation of reduced sulfur species to sulfate, with R p increasing to 65–145 kΩ·cm². The effect of reduced sulfur species is therefore transient and ends when the oxidation front reaches the reinforcement and oxidises all reduced sulfur species, a process that may take decades in some cases of GGBFS concretes, during which conventional corrosion criteria and the critical chloride threshold concept are not applicable to these systems.
Authors: Ali Nikoonasab, Thoralf Müller, Michael Raupach, Gregor J.G. Gluth
Language: English
Subfield: Civil and Structural Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,540
Funder: Deutsche Forschungsgemeinschaft
OpenAlex ID: W7204234728