Improvement of corrosion resistance of 316LN stainless steel by ultrasonic surface rolling process

316LN austenitic stainless steel (SS) with gradient structures was fabricated by the Ultrasonic Surface Rolling Process (USRP). Their pitting corrosion behavior was studied. The results reveal a dual effect induced by USRP: the pitting potential significantly increased from 0.14 to 0.46 V SCE , with the passive region expanded by a factor of 2. These improvements are attributed to a 46.61 % enhancement in Cr 2 O 3 content within the passive film, a 10.38 % increase in film thickness, and a reduced defect density (13.4 % and 31.3 % decreases in N D and N A values). Here, N D and N A represent donor and acceptor densities in the Mott-Schottky test, respectively. Conversely, a 29.7 % increase in metastable pitting initiation frequency was observed. However, the enhanced repassivation capability (a 60 % elevation in E prot - E corr potential difference) effectively inhibited the transition to stable pit growth. Collectively, the USRP demonstrates a remarkable enhancement in the corrosion resistance of 316LN SS through passive film composition modification, structural optimization, and dynamic repassivation capability improvement.