The Influence of Water Concentration on High-Temperature Reactive Evaporation and Condensation of Cr in 800°C Air

Abstract

Reactive evaporation of Cr from stainless steels used in solid oxide electrochemical systems, such as solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) systems, is well-documented as the cause of Cr poisoning; however, the condensation and interactions of volatilized Cr species onto and with surrounding interfaces during complex and dynamic system exposures is less understood. Understanding these interactions during operation is critical for improving system performance and safeguarding environmental, health and safety, as some condensed Cr forms toxic hexavalent chromium (Cr(VI)) species. The objective of this study is to investigate and report on condensation pathways of Cr vapors within representative high-temperature system environments. To accomplish this objective, Cr vapors, produced by high-temperature (800°C) air exposures of trivalent chromium (Cr(III)) oxide (Cr2O3) powder with variable moisture content, were condensed onto various ceramic materials at lower temperatures (<400°C). Both the total amount of Cr and ratios of oxidation states were measured using ICP-MS and colorimetric analyses. An increase of Cr condensation was observed with increased water content, with similar Cr(VI) to Cr(III) ratios. Results and interpretations are discussed in context of improved understanding of Cr reactive evaporation and condensation in SOFC/SOEC and related high-temperature materials and systems.