Corrosion of 304 stainless steel in molten-carbonate fuel cells

The corrosion behavior of 304 stainless steel was characterized with cyclic voltammetry in a eutectic Li/K and Li/Na carbonate melt under anode and ca thode gas of the molten-carbonate fuel cell (MCFC). The corrosion rate of 3 04 steel was determined in four different environments of the MCFC with ele ctrochemical methods and from cross-sectional analysis of corrosion layers. These four environments were open-circuit and MCFC-load conditions both un der anode and cathode gas. At open-circuit conditions corrosion was more se vere under the oxidizing cathode gas than under the reducing anode gas. On the contrary, at load conditions corrosion was more severe under anode than under cathode gas. The anodic polarization under anode gas enhances corros ion, whereas the high anodic polarization under cathode gas leads to anodic protection. Corrosion currents were measured with chronoamperometry and de termined with Tafel extrapolation from quasi-stationary polarization-curve measurements. The difference between the corrosion layer thickness estimate d from these corrosion currents and the corrosion layer thickness determine d from cross-sectional analysis is mainly due to contributing currents of e ither the MCFC-anode gas reaction under anode gas or the MCFC-cathode gas r eaction under cathode gas. (C) 1999 The Electrochemical Society. S0013-4651 (98)10-018-6. All rights reserved.