Influence of temperature and lithium purity on corrosion of ferrous alloys in a flowing lithium environment

Abstract

Corrosion data have been obtained on ferritic HT-9 and Fe-9Cr-lMo steel and austenitic Type 316 stainless steel in a flowing lithium environment at temperatures between 372 and 538°C. The corrosion behavior is evaluated by measurements of weight loss as a function of time and temperature. A metallographic characterization of materials exposed to a flowing lithium environment is presented. INFLUENCE OF TEMPERATURE AND LITHIUM PURITY ON CORROSION OF FERROUS ALLOYS IN A FLOWING LITHIUM ENVIRONMENT K. Chopra and D. L. SmithMaterials Science and Technology Division Argonne National Laboratory. Argonne, IL 60439, U.S.A. IntroductionLiquid lithium is an attractive first wall/blanket material for fusion reactors because of its efficient heat transfer properties and acceptable tritium-breeding characteristics. A major concern arising from the use of lithium is its compatibility with the containment material. The corrosion behavior of several ferritic and austenitic steels has been investigated in thermal-and forced-circulation lithium loops [1][2][3][4][5][6][7][8][9][10]. Data on corrosion/mass transfer in liquid lithium systems have been reviewed to identify the influence of various material and system parameters on corrosion [11][12][13]. The results indicate that mass transfer and deposition most likely will determine the maximum operating temperature in liquid lithium blanket systems. The ferritic HT-9 alloy and Fe-9Cr-lMo steel exhibit better resistance to corrosion in lithium than the austenitic steels, such as Type 316 stainless steel (SS). However, available data are insufficient to quantify the influence of system parameters, e.g., temperature, flow velocity, system temperature gradient (AT), lithium purity, etc., on corrosion and to estimate the maximum operating temperature limits for liquid lithium systems. This paper presents information on the corrosion behavior of several ferrous alloys in a flowing lithium environment at temperatures between 372 and 538°C. The effects of temperature and lithium purity on corrosion are discussed.-2- Experimental ProcedureThe corrosion tests were conducted In a forced-circulation lithium loop consisting of three test vessels and a secondary cold-trap purification loop. A detailed description of the lithium loop has.been presented earlier [1]. Flat corrosion specimens, ~70 x 10 x 0,3 mm in size, of ferritic HT-9 and Fe-9Cr-lMo steels and austenitic Type 316 SS were exposed to flowing lithium, and the corrosion behavior was evaluated from measurements of weight loss and the depth of internal corrosion (or thickness of the ferrite layer for austenitic steels). The chemical composition of the materials is given in Results Ferritic steelsThe weight losses for HT-9 and Fe-9Cr-lMo steels exposed to flowing lithium at 372, 427, 482, and 538°C are shown in fig. 1. The results indicate that after a relatively large weight loss durig the initial 500-h exposure to lithium, the weight losses for ferritic steels follow a linear law with time -3-and yield a constant dissolution ...

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