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Improvement on the pitting corrosion resistance of 304 stainless steel via duplex passivation treatment
Author(s) -
Hou Yan,
Zhao Jie,
Cao TieShan,
Zhang Lei,
Meng XianMing,
Zhang ZhiPeng,
Cheng CongQian
Publication year - 2019
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201910892
Subject(s) - passivation , dissolution , materials science , corrosion , pitting corrosion , electrolyte , x ray photoelectron spectroscopy , dielectric spectroscopy , oxide , polarization (electrochemistry) , metallurgy , electrochemistry , chemical engineering , electrode , chemistry , composite material , layer (electronics) , engineering
A remarkable improvement in the pitting corrosion resistance of 304 stainless steel was attempted using a novel duplex passivation treatment method. First, chemical passivation in nitric acid followed electrochemical passivation via potential polarization of step cycling in sodium nitrate electrolyte. Compared with traditional chemical passivation, breakdown potential was increased from 0.31 V SCE to positive than 0.9 V SCE at 70°C in a solution bearing 0.6 M [Cl − ] concentration. The critical pitting temperature was enhanced from 21.5°C to above 70°C in a solution with 6 M [Cl − ] concentration. Impedance analysis and X‐ray photoelectron spectroscopy results show that a more compact passive film with a higher ratio of chromium oxide on iron oxide was achieved by electrochemical passivation compared with chemical passivation. Morphology observation suggested that the potential polarization of step cycling slightly increased the dissolution of inclusions after being subjected to chemical passivation. The probable reason for the improvement on pitting resistance is discussed in detail based on inclusion dissolution and the protectiveness in passive film.