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Zairyo-to-Kankyo Vol. 68 (2019), No. 6

ISIJ International
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ONLINE ISSN: 1881-9664
PRINT ISSN: 0917-0480
Publisher: Japan Society of Corrosion Engineering

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  1. Vol. 73 (2024)

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Zairyo-to-Kankyo Vol. 68 (2019), No. 6

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Article Title

Imperial Era Name, from Heisei to Reiwa

Development of New Corrosion Test Equipment Simulating Sulfuric Acid Decomposition Gas Environment in a Thermochemical Hydrogen Production Process

Noriaki Hirota, Seiji Kasahara, Jin Iwatsuki, Yoshiyuki Imai, Hirofumi Ohashi, Xing Yan, Yukio Tachibana

pp. 137-142

Abstract

New corrosion test equipment for high temperature gas of decomposed sulfuric acid was manufactured in order to ascertain flow rate of sulfuric acid in the piping, occurrence of sulfuric acid decomposition reaction in the equipment, and temperature distribution inside the furnace tube. The flow rate of the sulfuric acid solution was constantly measured using an ultrasonic flowmeter. The SO3 concentration at the inlet of the test equipment was almost the same as that at the inlet of the sulfuric acid decomposer in the hydrogen production plant assuming a high-temperature gas cooled reactor hydrogen-power cogeneration system(GTHTR300C). On the other hand, during a test, leakage of sulfuric acid occurred from the fitting part at the outlet side. Hence the temperature distribution of the fitting part at the outlet side was investigated using fluid analysis. As a result, it was found that the temperature at the fitting was low enough to use fluorine joint grease when the distance was 0.05 m or more away from the outlet side pipe. An improved furnace tube was manufactured and the temperature was measured again at fitting part of the outlet side. The temperature was lower that the temperature limit of the joint grease, and almost the same as the temperature distribution in the fluid analysis. Leakage of sulfuric acid has not occurred to date.

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Article Title

Development of New Corrosion Test Equipment Simulating Sulfuric Acid Decomposition Gas Environment in a Thermochemical Hydrogen Production Process

Nano-Scale Nitridation of Fine-grained Stainless Steel as Bipolar Plates for Proton Exchange Membrane Fuel Cells

Hironori Yusa, Hitoshi Yashiro, Masanobu Kumagai

pp. 143-147

Abstract

In expectation of nano-scale nitride layer formation, type 445J1 stainless steels with different grain sizes were cathodically charged in nitric acid-nitrate solution (ECN treatment) and evaluated in terms of interfacial contact resistance against carbon paper (ICR), anodic polarization behavior, chemical state of the surface and PEFC performance in use as bipolar plates. The ECN treatment reduced ICR with more pronounced effect for the stainless steel with finer grains. Polarization test revealed that corrosion resistance was not degraded by the ECN treatment. XPS analysis proved formation of nitride layer on the surface of the stainless steel. The nitride layer was thicker and more stable against anodic polarization for the stainless steel with finer grains. The ECN treatment was applied to the fine-grained stainless steel for use as bipolar plates. The cell performance was comparable to that with graphite bipolar plates, proving that the ECN treated type 445J1 stainless steel with fine grains is a promising candidate material for PEFC bipolar plates.

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Article Title

Nano-Scale Nitridation of Fine-grained Stainless Steel as Bipolar Plates for Proton Exchange Membrane Fuel Cells

Electropolishing of Niobium in a Sulfuric Acid Solution by Pulse Potential Control

Ryo Shiratori, Shoma Kawamura, Hitoshi Yashiro, Keisuke Nii, Yoshiaki Ida, Hideaki monjushiro

pp. 148-151

Abstract

Using a three-electrode system, effect of pulse period of controlled potential on the electropolishing behavior of Nb in 30 mass% H2SO4 was examined. The potential pattern consisted of cathodic pulse (-3 V vs. Ag/AgCl for tc), anodic pulse (+1 V vs. Ag/AgCl for ta) and rest time (0 V vs. Ag/AgCl for 1 ms). The results of various combinations of tc and ta showed that both tc and ta were needed to be longer than 0.5 ms for successful polishing. Good performance was obtained when each pulse was balanced and the etching rate became maximum for tcta= 2 ms. The surface observation indicated that small pits were generated in the early stage of polishing and extended to form dimpled faces. However shorter ta than tc resulted in rugged surface, suggesting mechanical damage of Nb matrix by hydrogen. Thus, the combination of tc and ta in good balance is important in this polishing.

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Article Title

Electropolishing of Niobium in a Sulfuric Acid Solution by Pulse Potential Control

Shape of Capsules Containing Healing Agent for Self-Healing Coating, by heat treatment

Yuki Tsuji, Haruka Okuyama, Haruno Yanagimoto, Atsushi Hyono, Makoto Chiba, Hideaki Takahashi

pp. 152-156

Abstract

In order to improve the self-healing property of coating, we try to produce spheroidal capsules by using precursor solutions, whose viscosity was increased by heat treatment. The spheroidal capsules can be obtained under agitation with low speed(300 rpm). The flattening coefficient of spheroidal capsule synthesized is about 0.7-0.9.

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Article Title

Shape of Capsules Containing Healing Agent for Self-Healing Coating, by heat treatment

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