Monitoring the near-surface pH to probe the role of nitrogen in corrosion behavior of low-temperature plasma nitrided 316L stainless steel.
PBN-AR
Instytucja
Instytut Chemii Fizycznej Polskiej Akademii Nauk
Informacje podstawowe
Główny język publikacji
en
Czasopismo
Electrochimica Acta
ISSN
0013-4686
EISSN
Wydawca
PERGAMON-ELSEVIER SCIENCE LTD
DOI
URL
Rok publikacji
2013
Numer zeszytu
Strony od-do
208-215
Numer tomu
104
Liczba arkuszy
Autorzy
(liczba autorów: 3)
Pozostali autorzy
+ 1
Słowa kluczowe
en
Stainless steel;
Nitriding;
Antimony microelectrode;
Near-surface pH;
Corrosion; Pitting
Streszczenia
Język
en
Treść
Low temperature plasma nitriding of stainless steels improves tribological properties and pitting resistance, but it can activate anodic dissolution in acidic solutions. This work aimed at determining how anodic behaviour can be affected by nitrogen present in the steel. The electrochemical behaviour of AISI 316L steel after nitriding at 415 °C (with up to 17 at.% N) was examined in solutions of 0.1 M Na2SO4 + 0.4 M NaCl acidified down to pH 2.4. An antimony microelectrode was used to measure pH close to the sample surface. It was found that the nitrided layer was resistant to pitting corrosion at all pH's, but at pH below about 3.5 anodic currents were higher than those on untreated steel. For nitrided steel the near-surface pH was increasing when anodic current was rising in the active region, evidently due to binding of protons into NH4+. Nitrided steel underwent reactivation during reverse cathodic sweeps which is characteristic of low content of chromium oxide in surface film. Injection of NH4OH into the solution improved the passivation. Thermodynamic data indicated that the accompanying pH rise enabled the formation of Fe3O4, Fe2O3, Cr2O3, FeCr2O4, NiFe2O4, MoO42− and NO2−. It is suggested that the pitting resistance of nitrided steel results from an easy repassivation of incipient pits due to the formation of the above species.
Cechy publikacji
ORIGINAL_ARTICLE
Inne
System-identifier
608826
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