The corrosion behaviour of mortar samples reinforced with three different types of ribbed stainless steel (SS) was tested after 9 years. The reinforcements had been both similar welded (SS-SS) and dissimilar welded to carbon steel (SS-CS). After welding, the bars were cleaned by pickling, although this treatment was unable to remove the welding oxides completely. The prepared reinforcements were then embedded in carbonated mortar with chlorides and exposed to high relative humidity. Corrosion potential and electrochemical impedance spectroscopy measurements were used to monitor the spontaneous corrosion behaviour of the samples over 8 years. The welded bars were then anodically polarised in order to force attack. Exposure was continued for a further year to allow progression of the pits. For the SS-SS welded samples, S20430-S20430 showed poor corrosion resistance under these conditions, whereas S32205-S32205 reinforcements demonstrated excellent corrosion behaviour.