A rapid corrosion screening technique for grade 2707 hyper-duplex stainless steel at ambient temperature

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.