Research on the pitting behavior of high nitrogen austenitic stainless steel 316LN in sodium chloride solution by using modified potentiostatic pulse test

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Vol. 922; p. 116739
• Main Authors: Chen, Si, Sun, Li, Cao, Wenkai, Zhao, Tianyu, Qiu, Jie, Li, Weihua
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.2022; Elsevier Science Ltd
• Subjects: Austenitic stainless steels; Corrosion resistance; Inclusions; Nitrogen; Oxidation; Passive film; Pitting; Pitting (corrosion); Potentiostatic pulse test; Silicon dioxide; Sodium chloride; Stainless steel; Pitting; Passive film; Inclusions; Potentiostatic pulse test
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/j.jelechem.2022.116739

•The modified potentiostatic pulse test is used to study the pitting behavior of 316LN.•The pitting size and number of 316LN are regulated.•The Si-enriched inclusions are initial sites of metastable pit on 316LN surface.•The pitting resistance of 316LN is enhanced after the potentiostatic pulse test. The pitting behavior of high nitrogen austenitic stainless steel 316LN was studied by using the modified potentiostatic pulse test (PPT). The results show that the duration of the high potential (Eh) and the low potential (El) significantly affect the pitting size and number of 316LN. However, the pitting behavior of 316LN only changes during the first five pulse cycles, because the metastable pitting initiates at the limited inclusions. The optimal PPT condition is regarded as Eh = 0.5 VSCE for 1 s, E1 = 0.2 VSCE for 2 s and ten pulse cycles. Metastable pits initiate at the susceptible sites of inclusions which are identified as SiO2 and SiC. The metastable pits will further grow or restrain with the increasing time of Eh or El, respectively. After PPT modification, the pitting resistance of 316LN is enhanced due to the removal of the Si-enriched inclusions from the 316LN surface. Meanwhile, the fewer current transitions, the lower passivation current density and the higher impedance all suggest that the protectiveness of the oxidation film formed on 316LN surface is improved after PPT.