Microelectrochemical Investigation of Anodic Polarization Behavior of CrS Inclusions in Stainless Steels

Muto, Izumi; Kurokawa, Shimpei; Hara, Nobuyoshi

doi:10.1149/1.3223997

Cited by 46 publications

(56 citation statements)

References 32 publications

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“…13 are in good agreement with the work of Muto et al, who demonstrated that the composition of (Mn,Cr)S inclusions changes, becoming Cr-rich under anodic polarization, and that oxide films form on the inclusions. 27 Lillard et al also observed Cu deposition on the MnS surface immersed in 0.1 M NaCl. 25 The results of the SEM/EDS analysis presented in Figs.…”

Section: Effect Of Electrode Size On Pit Initiation-comparison Ofmentioning

confidence: 91%

Local Electrochemistry and In Situ Microscopy of Pitting at Sensitized Grain Boundary of Type 304 Stainless Steel in NaCl Solution

Ida

Muto

Sugawara

et al. 2017

J. Electrochem. Soc.

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To elucidate the pit initiation behavior of sensitized stainless steels, the anodic polarization of a single grain boundary was examined in 0.1 M NaCl (pH 5.4) at 298 K using a micro-electrochemical system. For Type 304 heat-treated at 923 K for 2 h, no pitting was initiated on a small area (ca. 100 μm × 100 μm) with a sensitized grain boundary without MnS inclusions. However, stable pitting was observed on the electrode area that was larger than ca. 200 μm × 200 μm. In situ microscopy revealed that the first step in corrosion was a spherical pit generated at a MnS inclusion at a sensitized grain boundary, and that intergranular corrosion started at the pit. The local depassivation of the Cr-depleted zone along the sensitized grain boundary was thought to be introduced by the dissolution of the inclusion. The co-existence of the MnS inclusion and the Cr-depleted zone was considered to be the critical factor in the pit initiation of sensitized stainless steels in NaCl solutions. Stainless steels are widely used in chloride environments because of their high corrosion resistance, which is attributed to their high Cr content, at above 12 mass%.1 When stainless steels are heated to around 900 K (e.g., welding), sensitization occurs due to the formation of Cr-depleted zones at the grain boundaries. The susceptibility to intergranular corrosion and pitting at the grain boundaries increases as a result of sensitization-treatments. 2To assess the degree of sensitization and/or the mechanisms of intergranular corrosion, acidic solutions are usually used. ASTM A262 testing specification contains the following intergranular corrosion tests: 1) Huey test (boiling HNO 3 ), 2) Strauss test (boiling H 2 SO 4 + CuSO 4 + metallic Cu), 3) and Streicher test (boiling H 2 SO 4 + Fe 2 (SO 4 ) 3 ). After immersion, the specimens are visually examined and/or measured for weight loss. These methods have been widely and successfully used in corrosion engineering. ISO 12732 specifies a method that uses the double loop electrochemical potentiodynamic reactivation test (based onĈihal's method 3 ). In this method, the standard solution is 0.5 M H 2 SO 4 -0.01 M KSCN, and the degree of sensitization can be evaluated quantitatively from the comparison of the peak current densities between the anodic scan and the subsequent cathodic scan.Although acidic solutions are generally used to evaluate the degree of sensitization, in practical applications, pitting and stress corrosion cracking occur in stainless steels in near-neutral pH environments. NaCl solutions are used to evaluate the pitting corrosion resistance and the susceptibility of sensitized stainless steels to stress corrosion cracking (SCC). Cheng et al. studied the pitting corrosion of sensitized Type 304 stainless steel under wet-dry cycling and demonstrated that both the probability of pitting and the average size of the pit increased as a result of sensitization. 4 It was suggested that the observed change in the pit morphology from round to an irregular shape could be attributed t...

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Section: Effect Of Electrode Size On Pit Initiation-comparison Ofmentioning

confidence: 91%

Local Electrochemistry and In Situ Microscopy of Pitting at Sensitized Grain Boundary of Type 304 Stainless Steel in NaCl Solution

Ida

Muto

Sugawara

et al. 2017

J. Electrochem. Soc.

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“…Figure 12 shows the microscopic polarization curves for the small areas of austenitic stainless steels with MnS, CrS, and Ti 4 C 2 S 2 inclusions in NaCl solutions at 298 K. The polarization curves for MnS and CrS were quoted from the literature. 20 As shown in this figure, the MnS inclusion dissolved in the passive region of stainless steels in 0.5 M NaCl, and pit initiation occurred. The CrS inclusion did not dissolve in the passive region of stainless steels, but pitting was initiated at the inclusion at higher potentials because of the transpassive dissolution of Cr-oxide film on the inclusion surface.…”

Section: Comparison Of Pit Initiation Resistance At the Inclusionsmentioning

confidence: 69%

“…The CrS inclusion did not dissolve in the passive region of stainless steels, but pitting was initiated at the inclusion at higher potentials because of the transpassive dissolution of Cr-oxide film on the inclusion surface. 20 In contrast, no pitting was observed at the Ti 4 C 2 S 2 inclusions even in 3 M NaCl. There is no current increase due to the inclusions dissolution and pitting in the polarization curve for the small area with the Ti 4 C 2 S 2 inclusions.…”

Section: Comparison Of Pit Initiation Resistance At the Inclusionsmentioning

confidence: 94%

Microscopic Polarization Behavior and Thermodynamic Stability of TiS and Ti₄C₂S₂ Inclusions in Stainless Steels

et al. 2013

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Microelectrochemical polarization, thermodynamic calculations, and Auger electron spectroscopy were performed to elucidate the predominant factor affecting the pit initiation resistance at sulfide and carbosulfide inclusions in stainless steels. The Ti-oxide enriched layers on the inclusions inhibit the dissolution of the TiS and Ti 4 C 2 S 2 inclusions in the passive and trans-passive regions of stainless steels. While the MnS inclusion surfaces are covered by Mn-oxides, the corrosion resistance of Mn-oxides is not sufficient to prevent the inclusion dissolution and pit initiation. The oxide enriched surface layers on the sulfide and the carbosulfide inclusions greatly influence the pit initiation resistance at the inclusions.

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“…[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] After the anodic polarization (Fig. As many researchers have already pointed out, the current increase around 0.6 V is due to the anodic dissolution of MnS inclusions and stable pit initiation at the inclusions.…”

Section: Resultsmentioning

confidence: 93%

Local Dissolution of MnS Inclusion and Microstructural Distribution of Absorbed Hydrogen in Carbon Steel

Shinozaki¹,

Muto²,

Omura³

et al. 2011

J. Electrochem. Soc.

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Microelectrochemical polarization and silver decoration techniques were performed on a small area with and without MnS inclusions in carbon steel. The surfaces of the inclusions were found to have partially dissolved in the potential range from 0.35 to À0.25 V (vs. SHE) in a boric-borate buffer (pH 8.45) solution with 10 mM NaCl, whereas the entire surface of the inclusions was slightly dissolved below and above this potential range. Silver deposition occurred only on and around MnS inclusions below 0.0 V, which generally corresponded to the stable region of hydrogen sulfide ions. When the inclusion surfaces were partially dissolved, silver deposition was observed only in the dissolved area. The dissolution species from MnS inclusions appeared to have promoted the hydrogen absorption reaction.

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Microelectrochemical Investigation of Anodic Polarization Behavior of CrS Inclusions in Stainless Steels

Cited by 46 publications

References 32 publications

Local Electrochemistry and In Situ Microscopy of Pitting at Sensitized Grain Boundary of Type 304 Stainless Steel in NaCl Solution

Local Electrochemistry and In Situ Microscopy of Pitting at Sensitized Grain Boundary of Type 304 Stainless Steel in NaCl Solution

Microscopic Polarization Behavior and Thermodynamic Stability of TiS and Ti₄C₂S₂ Inclusions in Stainless Steels

Local Dissolution of MnS Inclusion and Microstructural Distribution of Absorbed Hydrogen in Carbon Steel

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Microelectrochemical Investigation of Anodic Polarization Behavior of CrS Inclusions in Stainless Steels

Cited by 46 publications

References 32 publications

Local Electrochemistry and In Situ Microscopy of Pitting at Sensitized Grain Boundary of Type 304 Stainless Steel in NaCl Solution

Local Electrochemistry and In Situ Microscopy of Pitting at Sensitized Grain Boundary of Type 304 Stainless Steel in NaCl Solution

Microscopic Polarization Behavior and Thermodynamic Stability of TiS and Ti4C2S2 Inclusions in Stainless Steels

Local Dissolution of MnS Inclusion and Microstructural Distribution of Absorbed Hydrogen in Carbon Steel

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Microscopic Polarization Behavior and Thermodynamic Stability of TiS and Ti₄C₂S₂ Inclusions in Stainless Steels