High Temperature Corrosion Of Separator Materials For Mcfc

Masahiro Yanagida, Kazumi Tanimoto, Toshikatsu Kojima, Yukiko Tamiya, Takashi Asai and Yoshinori Miyazaki Osaka National Research Institute 1-8-31 Midorigaoka, Ikeda, Osaka 563, Japan

1. Introduction

The Molten Carbonate Fuel Cell (MCFC) is one of promising high efficiency power generation devices with low emission. Molten carbonate used for its electrolyte plays an important role in MCFC. It separates between anode and cathode gas environment and provides ionic conductivity on MCFC operation. Stainless steel is conventionally used as separator/current collector materials in MCFC cathode environment. As corrosion of the components of MCFC caused by the electrolyte proceeds with the electrolyte consumption, the corrosion in the MCFC is related to its performance and life. To understand and inhibit the corrosion in the MCFC is important to realize MCFC power generation system.

We have studied the effect of alkaline earth carbonate addition into carbonate on corrosion of type 316L stainless steel15. In this paper, we describe the effect of the temperature on corrosion behavior of type 316L stainless steel with carbonate mixture, (Lio^Kojg^COa, under the cathode environment in out-of-cell test.

2. Experimental

The commercially available type 316L stainless steel (SUS316L) sheet, which is 0.5 mm in thickness, was served as corrosion specimen. Its chemical composition is listed in table 1. The plate was cut into 10 x 20 mm, polished with wet #1000 abrasive paper, washed, degreased by acetone, rinsed with distilled water, and dried. Reagent grade Li2C03 and K2C03, which purity was > 99.0% and > 99.5%, respectively, were served for preparation of mixed carbonate. Mixed carbonate composed of Li2C03 : K2C03 = 62 : 38 (mol%) was melted at 650 °C under pure C02 environment, quenched and ground prior to coating. Specimens were coated with the mixed carbonate of 5 mg/crn2 and hung in an alumina crucible. Corrosion test was carried out under the ambient cathode environment (C02/02 = 2/1) at 600, 650, 700 °C in out-of-cell. After the corrosion test, weight gain due to corrosion was measured by removing carbonate. In order to investigate the corrosion behavior, tested corrosion specimens after removing deposit by distilled water were analyzed by X-ray diffraction (XRD) and electron probe micro-analysis (EPMA).

YANAGIDA et. al.

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