AbstractIn this study Mode IV‐corrosion fatigue (CF) characterized by additional superposition of pitting corrosion was investigated. Corrosion fatigue and polarization experiments were carried out on three austenitic (17Cr–13Ni–5Mo–0.15N, 25Ni–20Cr–5Mo–1.5Cu and 18Cr–10Ni–2Mo–0.5Ti) stainless steels in 0.05 M sulphuric acid to which 20000 ppm Cl−was added. The CF strength decreased drastically when Mode IV‐conditions apply. The damaging effect of pitting corrosion in Mode IV was very pronounced. The relation between pitting, repassivation of the pits and Mode IV‐CF was investigated and it was found that for rotaing beam CF the measured repassivation potential represents a conservative upper boundary value below which mode II‐CF (i.e. CF under stable passivity) replaces Mode IV‐CF, when operating below stress ranges of 75% of the fat