Corrosion and Passivation of High Nitrogen Face-Centered-Cubic Phase Formed on AISI 304L Austenitic Stainless Steel in Borate Buffer Solution

Wang, K. S.; Song, Tong; Lei, Ming

doi:10.1149/2.0971510jes

Cited by 11 publications

(10 citation statements)

References 40 publications

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“…Wang et al reported similar results with austenitic stainless steels: the passive current density of the plasma nitrided stainless steel in a borate buffer solution at pH 8.4 was reported to be one tenth that of untreated stainless steel. 34 The difference between the passive current density of the untreated carbon steel and the nitrogen solid solution layer in the buffer solution at pH 8.45 suggests that, besides alkalization (OH − ions), the other dissolution products of interstitial nitrogen, such as NO 3 − ions, had an effect on the anodic polarization behavior of the nitrogen solid solution layer.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Aspects of Interstitial Nitrogen in Carbon Steel: Passivation in Neutral Environments

Chiba

Nagataki

Nishimura

2016

J. Electrochem. Soc.

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Plasma nitriding treatment was applied at 603 K to introduce interstitial nitrogen into carbon steel and to form a precipitation free nitrogen solid solution layer. The nitrogen solid solution layer contained 0.05-0.1 mass% (0.2-0.4 at%) interstitial nitrogen and resulted in ca. 0.7% expansion of the lattice parameter. Anodic polarization measurements of the nitrogen solid solution layer were taken to reveal the effect of interstitial nitrogen on the polarization behavior of carbon steel. The nitrogen solid solution layer was passivated in Na 2 SO 4 solutions above pH 6.0. The effectiveness of alkalization and NO 3 − ions, which were the expected dissolution by-products or products of interstitial nitrogen, was confirmed using buffer solutions at pH 6.0 and 8.45 with and without NO 3 − ions. In addition, the work function of carbon steel increased 0.08 eV with the interstitial nitrogen, suggesting the interstitial nitrogen made it difficult for the carbon steel to dissolve into solutions. Therefore, it was concluded not only did the interstitial nitrogen affect the exposed environments due to the alkalization and NO 3 − ions, but also that the work function of the carbon steel changed. The combination of these three factors resulted in the passivation of the nitrogen solid solution layer in a neutral environment. Interstitial nitrogen and carbon have been reported to successfully improve the corrosion resistance of iron-based metals. Because the solid solubility limits of nitrogen and carbon in austenite phase is higher than those in the ferrite and martensite phases, interstitial elements are typically used in austenitic stainless steels. Low temperature plasma nitriding treatments have been known to result in the formation of a precipitation free nitrogen super saturated solid solution layer on austenitic stainless steels. These are characterized by a crystal structure similar to that of face centered cubic (fcc) austenite with interstitial nitrogen, and are known to exhibit high localized corrosion resistance. Many researchers have demonstrated that plasma nitriding treatments below 723 K form a precipitation free nitrogen solid solution layer which results in the improvement of pitting and crevice corrosion resistance, whereas plasma nitriding treatments above 723 K form nitride precipitates, such as chromium nitride (CrN), in a nitrogen solid solution layer and decrease corrosion resistance.1-6 Other nitriding treatments without nitride precipitates, such heat-treatment in a nitrogen atmosphere and a nitrogen gas pressurized electro-slag remelting process, also improve the pitting corrosion resistance of austenitic stainless steels. 7,8 Baba et al. detected ammonia (NH 3 ) as a dissolution product of interstitial nitrogen in austenitic stainless steels by absorptiometry, and proposed that the hydroxide ions (OH − ) generated as a by-product of the NH 3 production reaction improved the localized corrosion resistance of austenitic stainless steels with interstitial nitrogen. 7 In an experiment on a low temper...

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Section: Resultsmentioning

confidence: 99%

Electrochemical Aspects of Interstitial Nitrogen in Carbon Steel: Passivation in Neutral Environments

Chiba

Nagataki

Nishimura

2016

J. Electrochem. Soc.

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“…It has been hypothesized that the lower donor density in the outer n-type iron oxide/hydroxide region decreases the pitting nucleation ability, hindering the chloride-ion adsorption [225]. A decrease of donor and acceptor densities and of the corresponding flat band potential has also been observed for nitrided AISI 304L tested in borate buffer solution at pH 8.4 [242].…”

Section: Semiconducting Properties Of the Passive Filmmentioning

confidence: 97%

From Austenitic Stainless Steel to Expanded Austenite-S Phase: Formation, Characteristics and Properties of an Elusive Metastable Phase

Borgioli

2020

Metals

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Austenitic stainless steels are employed in many industrial fields, due to their excellent corrosion resistance, easy formability and weldability. However, their low hardness, poor tribological properties and the possibility of localized corrosion in specific environments may limit their use. Conventional thermochemical surface treatments, such as nitriding or carburizing, are able to enhance surface hardness, but at the expense of corrosion resistance, owing to the formation of chromium-containing precipitates. An effective alternative is the so called low temperature treatments, which are performed with nitrogen- and/or carbon-containing media at temperatures, at which chromium mobility is low and the formation of precipitates is hindered. As a consequence, interstitial atoms are retained in solid solution in austenite, and a metastable supersaturated phase forms, named expanded austenite or S phase. Since the first studies, dating 1980s, the S phase has demonstrated to have high hardness and good corrosion resistance, but also other interesting properties and an elusive structure. In this review the main studies on the formation and characteristics of S phase are summarized and the results of the more recent research are also discussed. Together with mechanical, fatigue, tribological and corrosion resistance properties of this phase, electric and magnetic properties, wettability and biocompatibility are overviewed.

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“…The MS plots were explained as a p-type inner oxide layer and an n-type outer oxide layer based on the composition difference of the bilayered film in a microstructure respect. 11,19,20 This interpretation is different from the KP of passive Cr. For the KPs herein, it was concluded that they were closely related to the variation of the dc and that near where the second or first derivatives of I(E) were zero, the KPs usually occurred.…”

Section: Resultsmentioning

confidence: 82%

“…A KP is not common for an ideal semiconductor. However, this feature also commonly appears in the MS plots of some thin passive films, including those on iron, 5,6 nickel, 7,8 stainless steels, [9][10][11] and Ni-Cr-Mo alloys. [12][13][14] The KP of passive Cr has been attributed to the film oxidation of Cr 3+ to Cr 6+ .…”

mentioning

confidence: 99%

Rediscovering Mott-Schottky Plots: A Knee-point in the Plot for Passive Films on Chromium

Ren

Zhou

2017

J. Electrochem. Soc.

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In previous studies, there has been no consensus on the semiconducting properties of passive films on pure chromium by either photo-electrochemical analysis or Mott-Schottky (MS) analysis. In this work, a knee-point (KP), which is an exotic phenomenon in MS plots for some passive films, was found to be independent of the oxidation of Cr 3+ to Cr 6+ . This shiftable KP was observed for the first time, and a strong correlation between the KP and the corresponding direct-current variation of the film during the MS test was also found. The investigation of the capacitance-time relationship on the aging of passive films provided a rational interpretation of the KP for the film investigated. These findings demonstrated that the film formed on Cr was not an ideal semiconductor, and MS analysis was not applicable to the film. Chromium is an element widely used in stainless steel alloys and nickel-based alloys because of its excellent corrosion resistance due to its highly stable passive film. It is well known that the passive film consists of an Cr 2 O 3 inner layer and an Cr(OH) 3 outer layer. 1Numerous studies on the electronic properties of passive films have been reported. Recently, however, both p-type 2,3 and n-type 4 films were observed using MS analysis.For MS plots, we note that there is a knee-point (KP) (Fig. 1) where the slope changes from positive to negative at a higher anodic potential for the passive film on Cr. A KP is not common for an ideal semiconductor. However, this feature also commonly appears in the MS plots of some thin passive films, including those on iron, 5,6 nickel, 7,8 stainless steels, 9-11 and Ni-Cr-Mo alloys. 12-14 The KP of passive Cr has been attributed to the film oxidation of Cr 3+ to Cr 6+ . 6,13,15 The generation of excess cation vacancies due to oxidation leads to p-type semiconductive behavior, while the film resistance decreases accordingly because of the thinning of the inner layer. 13 However, in our work on Cr, Inconel 625 and C2000 showed that the impedance did not decrease when the film formation potential (E F ) was higher than the KP potential (E KP ). Similar results have also been reported on Alloy 22 in chloride solutions.14 Additionally, the dependence of impedance on E F for the passive 316L SS in borate buffer 16 was not consistent with either n-type 17,18 or with mixed-type. (For example, MS plots presented an M-shape obtained by some authors.) 6,19,20 Recently, we observed that the KP for a film could shift in both the anodic and cathodic directions under varying test conditions. This raises question about the semiconducting property, because if the KP shifts to a negative potential direction, the plot presents a p-type character; otherwise, it presents an n-type character. In this paper, KPs in MS plots of passive films on Cr in 0.05 M H 2 SO 4 were studied in detail using conventional electrochemical methods: potentiostatic polarization, MS analysis, electrochemical impedance spectroscopy (EIS), and I-E fixed sampling. The new phenomenon observed was analyzed ...

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Corrosion and Passivation of High Nitrogen Face-Centered-Cubic Phase Formed on AISI 304L Austenitic Stainless Steel in Borate Buffer Solution

Cited by 11 publications

References 40 publications

Electrochemical Aspects of Interstitial Nitrogen in Carbon Steel: Passivation in Neutral Environments

Electrochemical Aspects of Interstitial Nitrogen in Carbon Steel: Passivation in Neutral Environments

From Austenitic Stainless Steel to Expanded Austenite-S Phase: Formation, Characteristics and Properties of an Elusive Metastable Phase

Rediscovering Mott-Schottky Plots: A Knee-point in the Plot for Passive Films on Chromium

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