Stainless steels are finding increasing use as reinforcement in repair work with original carbon steel reinforcement as well as new construction in aggressive environments. This work examines the corrosion properties of austenitic stainless steels 304L, 316L and duplex stainless steels, S32101, S32205. Cast-in stainless rebars were tested alone and coupled to carbon steel rebars to investigate the influence on the corrosion rates of the carbon steel. Chlorides were added to the concrete in amounts ranging from 0.3 % to 3 % by mass of cement. The macro-cell current between stainless steels and carbon steel showed a galvanic effect at the beginning of the exposure but this declined to very low values after some time. No corrosion was detected on any of the stainless steel rebars in contact with the concrete after two years exposure outdoor. Moreover, the coupling of the carbon steel to a stainless steel was seen to only have a minor effect on the corrosion rate of the carbon steel, indicating that the stainless steel acted as a weak cathode in this environment.