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The pitting corrosion behaviour of 27%Cr–7%Ni (2707) hyper‐duplex stainless steel (HDSS) at ambient temperature has been assessed using a novel bipolar electrochemistry test set‐up. Application of this technique generates a linear potential gradient at the surface of the HDSS 2707 test piece, which allows assessment of the pitting corrosion behaviour at ambient temperature. Pit nucleation and associated growth kinetics can be obtained and characterised. To assess pitting corrosion in high‐alloyed HDSS, the normal bipolar test method had to be modified by superimposing an auxiliary potential. This new test set‐up was demonstrated by characterising the nucleation of pits and associated pit growth kinetics. The latter occurred either at austenite/ferrite interphase or inside ferrite phase, with pit growth within the ferrite phase in the HCl environment. [ABSTRACT FROM AUTHOR]

• Bipolar electrochemistry to probe localised corrosion in stainless steel rebars is introduced. • The full spectrum of anodic-to-cathodic corrosion response is accessible. • Pit growth kinetics and 3D pit ratio development are reported. • Trans-passive corrosion and selective phase dissolution are observed and discussed. The corrosion performance of stainless steel rebars is assessed by using bipolar electrochemistry. This method produces a quasi-linear potential gradient across the sample, with the technique providing rapid access to test for the nucleation and growth of pits across a wide range of applied potentials. The localised corrosion behaviour and resulting growth kinetics of Types 304L and 316L austenitic stainless steels (ASSs) are compared to Type 2101 and 2205 duplex stainless steels (DSSs). The difference in selective phase dissolution between pitting and trans-passive corrosion in DSSs is compared, with critical pitting potential, pit nucleation numbers, growth kinetics, volume loss, and aspect ratio of these four stainless steels discussed. [ABSTRACT FROM AUTHOR]