Effects of Hydrogen Peroxide on Intergranular Stress Corrosion Cracking of Stainless Steel in High Temperature Water, (IV) Effects of Oxide Film on Electrochemical Corrosion Potential.

Abstract

In order to determine. the effects of hydrogen peroxide on electrochemical corrosion potential (ECP) of type 304 stainless steel (SUS304), ECPs were measured using a high temperature, high pressure water loop with polytetrafluoroethylene (PTFE) inner liner at controlled hydrogen peroxide concentration. It is observed that the ECP of SUS304 exposed to hydrogen peroxide is higher than that when exposed to oxygen at the same oxidant concentration. The ECP shows a hysteresis pattern for its concentration dependency. Those results were attributed mainly from the chemical form of oxide film on stainless steel specimens. The oxide film was affected by the corrosive circumstances. Hematite (a-Fe203) was observed for the specimens exposed to hydrogen peroxide, while Fe304 was a main oxide when exposed to oxygen. The difference of the anodic polarization curves between 02 and H202 environments was caused by the difference of the stability between a-Fe203 and Fe304. Since the a-Fe20 3 is reduced to the Fe 2 + when hydrogen is added to water, the ECP decreases with decreasing oxidant concentration without showing the hysteresis that keep the ECP higher value.

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

“…1,2) To determine the effects of H 2 O 2 , O 2 and their mixture on electrochemical corrosion potential (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. [3][4][5][6][7] From in situ measurements, i.e., ECP and frequency dependent complex impedance (FDCI), made in previous papers, [7][8][9] the authors confirmed the following. (1) The ECP and FDCI data of the 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 .…”

“…The thickness of oxide film on the specimen exposed to 100 ppb H 2 O 2 for 300 h was about 0.3 mm, while it was about 0. 5 Fig. 4 Electric resistance of oxide film obtained from Cole-Cole plots sion due to less oxidant.…”

Water Chemistry in a Crack Tip under Irradiation, (II)

“…6,7) Hydrogen peroxide (H 2 O 2 ) is one the most important radiolytic species to determine the corrosion environment of BWR primary cooling systems. 4,[8][9][10][11] In order to estimate the H 2 O 2 concentration in the crack tip water, decomposition rates of H 2 O 2 in the crack tip water and at the inner surface are important. In order to consider a large decomposition coefficient of H 2 O 2 at the crevice inner surface, it was assumed that the rate constant for the decomposition reaction of H 2 O 2 in the crevice surface region was 100 times as large as that in the crevice water region.…”

Influence of pre-deformation and oxidation in high temperature water on corrosion resistance of type 304 stainless steel

“…According to the analysis and structural investigation, the outermost part of the oxide film was [6]. Wada et al [7] found that the dominant phase in the oxide film formed on 304 stainless steel exposed to 288 °C water containing 1 ppm O 2 was magnetite type spinel. The study of Panter et al [8] revealed that the oxide film formed on Alloy 600 in simulated PWR primary water was composed of outer loosely packed spinel particles and inner compact Cr-rich layer.…”