Corrugated stainless steels embedded in carbonated mortars with and without chlorides: 9-Year corrosion results

• 5 corrugated stainless steels are studied in carbonated mortars.
• Corrosion synergies between carbonation and chlorides are analyzed.
• S32205 duplex shows no corrosion even at high polarizations.
• Partial immersion promotes higher corrosion rates than in non-carbonated mortars.

The corrosion behavior of 5 corrugated stainless steel bars was evaluated in carbonated mortars: UNS S20430, S30400, S31603, S31635 and S32205. The tests were carried out under 3 different exposure conditions: at high relative humidity (C-HRH); partially immersed in 3.5% NaCl (C-PI); and with CaCl2 added during mortar mixing and exposed to high relative humidity (C-HRHCl). Corrosion potential (Ecorr) measurements and electrochemical impedance spectroscopy (EIS) were used to monitor the behavior during the first 8 years of exposure. Then, anodic polarization tests were carried out and the exposure was extended for another additional year. Stainless steels do not corrode in carbonated conditions without chlorides, but some grades can suffer localized corrosion if they are submitted to high anodic polarizations. Low-Ni, austenitic S20430 corrugated bars are especially prone to suffer a low-intensity corrosive attack in carbonated mortars with chlorides. Moreover, the corrosion rate of S20430 bars can easily increase under moderate anodic polarizations. Duplex S32205 is immune to corrosion in the carbonated mortar with chlorides, even in partial immersion conditions and under high anodic polarizations.