Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (II) Optimization of Crack Propagation Rate Measurement System.

Self Cite

Corrosive conditions in BWRs are determined mainly by hydrogen peroxide (H 2 O 2 ). Then, a high temperature, high-pressure H 2 O 2 water loop was fabricated to identify the effects of H 2 O 2 on corrosion and stress corrosion cracking of stainless steel.By changing concentrations of H 2 O 2 and O 2 , in situ measurements of electrochemical corrosion potential (ECP) and frequency dependent complex impedance of test specimens were carried out and then characteristics of oxide film on the specimens were determined by multilateral surface analyses, i.e., laser Raman spectroscopy and secondary ion mass spectroscopy. The following points were experimentally confirmed.(1) The hematite ratio in the oxide films of the specimens exposed to H

Section: Introductionsupporting

confidence: 67%

Section: Multilateral Surface Analysesmentioning

confidence: 99%

Effects of Hydrogen Peroxide on Corrosion of Stainless Steel, (IV) Determination of Oxide Film Properties with Multilateral Surface Analyses

Miyazawa¹,

Uchida²,

Satoh³

et al. 2005

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“…[5][6][7][8] The material used was SUS304 with the chemical composition listed in Table 1. Prior to machining, the material was solution treated (1, 323 K×30 min WQ) and highly sensitized (1, 023 K×100 min+773 K × 24 h).…”

Section: Materials and Heat Treatmentmentioning

confidence: 99%

“…[4][5][6] This determines the IGSCC environment of structural materials even though the measured O 2 concentration has been reduced below 10 ppb in HWC. 7,8) In order to protect structural materials from IGSCC, new water chemistry control is needed: it can effectively reduce H 2 O 2 concentration or moderate the IGSCC regardless of the presence of a high concentration level oxidant, such as H 2 O 2 in reactor water. Alkaline water chemistry (AWC) has been studied in this work to find a way to meet the above requirement.…”

Section: Introductionmentioning

confidence: 99%

Mitigation Effect of Alkaline Water Chemistry upon Intergranular Stress Corrosion Cracking of Sensitized 304 Stainless Steel.

Wada

Tachibana

Uetake

et al. 2001

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Alkaline water chemistry (AWC) has been studied as a new water chemistry control to mitigate intergranular stress corrosion cracking (IGSCC) of sensitized type 304 stainless steel (SUS304). The AWC was found to be capable of reducing crack growth rates (CGRs) of the IGSCC. At first, the direct effect of AWC upon IGSCC was studied experimentally. The 1/4T compact tension specimen was used for measurement of CGRs of the SUS304 in high temperature and high purity water. Crack length was monitored by a reversing direct current potential drop method. The CGR of SUS304 at 400 ppb O 2 concentration was reduced ten-fold when solution pH was increased to 9. During this time, electrochemical corrosion potential (ECP) of the specimen did not change so much. Second, it was predicted by a radiolysis calculation that the AWC would reduce H 2 O 2 concentration under the hydrogen water chemistry (HWC). Since the H 2 O 2 concentration was more effectively suppressed by AWC, the required hydrogen concentration in feedwater to lessen the ECP of the reactor components was lower in AWC than at neutrality. Therefore, an indirect effect, that is moderation of the corrosive environment, could also be expected in addition to the direct moderation effect under HWC condition.

“…[5][6][7][8][9][10][11] To determine the effects of H 2 O 2 , O 2 and their mixture on ECP of type 304 stainless steel, the authors fabricated a high temperature, high-pressure water loop with a polytetrafluoroethylene (PTFE) inner liner, which minimized H 2 O 2 decomposition and lowered possible oxygen concentration. [7][8][9][10][11][12][13][14][15] From in situ measurements, i.e., ECP and frequency dependent complex impedance (FDCI), and surface characterization of oxide film on specimens made in previous papers, [12][13][14][15][16] the authors confirmed the following. (1) The ECP and FDCI data of the type 304 stainless steel specimens exposed to 100 ppb H 2 O 2 were not affected by co-existing O 2 with the same level oxidant concentration and they were also not affected by pre-exposure to 200 ppb O 2 .…”

Section: Introductionmentioning

confidence: 99%

Effects of Hydrogen Peroxide on Corrosion of Stainless Steel, (V) Characterization of Oxide Film with Multilateral Surface Analyses

Miyazawa

Terachi

Uchida

et al. 2006

Self Cite

In order to understand corrosion behavior of stainless steel in BWR reactor water conditions, characteristics of oxide films on stainless steel specimens exposed to H 2 O 2 and O 2 in high temperature water were determined by multilateral surface analyses, i.e., SEM (scanning electron microscope), LRS (laser Raman spectroscope), SIMS (secondary ion mass spectroscope) and STEM-EDX (scanning transmission electron microscope). The following points were experimentally confirmed.(1) Oxide layers were divided into inner and outer layers: Outer layers of the specimen exposed to 100 ppb H 2 O 2 consisted of larger corundum type hematite (-Fe 2 O 3 ) particles, while inner layers consisted of very fine Ni rich magnetite (Fe 3 O 4 ). Outer layers of the specimen exposed to 200 ppb O 2 consisted of larger magnetite mixture particles, while inner layers consisted of fine Cr rich magnetite.(2) Outer oxide layers consisted of oxide particles. The oxide particles depositing on the specimens exposed to 100 ppb H 2 O 2 were divided into two groups, i.e., a larger particle group and a smaller particle group. For other specimens, the diameter distribution of depositing particles was a single peak. Particle density and size were changed by oxidant concentration.