Corrosion behaviour of a Low Ni austenitic stainless steel in carbonated chloride-polluted alkali-activated fly ash mortar

• Corrosion of a low nickel SS in carbonated alkali activated fly ash mortars.
• Severe conditions are induced by chloride penetration.
• Very good corrosion performance of this steel during a 650 day exposure.
• The corrosion performance of this steel is slightly worse than that of AISI 304.
• Higher protection against pitting attack offered by fly ash vs OPC mortars.

This study concerns the corrosion behaviour of a low nickel and AISI 304 austenitic stainless steels embedded in alkaline activated fly ash mortars. They were carbonated and exposed for 650 days to increasing amounts of chloride ions to simulate a highly corrosive environment. The corrosion process was monitored by applying the electrochemical impedance spectroscopy (EIS) technique and, at the end of the 650 day exposure, by recording polarization curves on selected steel bars. After slab breakage, observations for detection of pitting attack and analysis of the total and free chloride contents in the mortars were carried out. These tests and some results obtained in simulated mortar pore solutions indicated that the fly ash mortars offered the rebars a higher protection against pitting attack than ordinary Portland cement mortar. The tests also evidenced the very good performances of the less expensive low nickel stainless steel.