Stainless steels are rarely used in soil applications, as their corrosion performance in soil is generally poor. Localized corrosion attack is a particularly serious concern. The presence of halide ions and concentration cells developed on the surface of these alloys tend to induce localized corrosion damage.
The two most common mechanisms of reinforcing steel corrosion damage in concrete are:
Localized breakdown of the passive film by chloride ions
Carbonation, a decrease in pore solution pH leading to a general breakdown in passivity.
Harmful chloride ions usually originate from de-icing salts applied in cold climate regions or from marine type environments/atmospheres. Carbonation damage is predominantly induced by a reaction of concrete with carbon dioxide (CO2) in the atmosphere.
Chloride induced rebar corrosion tends to be a localized corrosion process, with the original passive surface being destroyed locally under the influence of chloride ions. Apart from the internal stresses created by the formation of corrosion products leading to cracking and spalling of the concrete cover, chloride attack ultimately reduces the cross section and significantly compromises the load carrying capability of steel reinforced concrete.