Influence of Water Concentration on High-Temperature Reactive Condensation of Chromium Vapors Generated in 800 °C Air

Abstract

Reactive evaporation of chromium (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. 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 species contain toxic hexavalent Cr (Cr(VI)). The objective of this study is to investigate the 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). The total amount of Cr and ratios of oxidation states were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES) and diphenyl carbazide (DPC) colorimetric / direct UV-VIS spectrophotometer analyses. Increased Cr condensation was observed with increased water content, with similar Cr(VI) to total Cr ratios. Results and interpretations are discussed in context of improving understanding of Cr reactive condensation in SOFC/SOEC and related high-temperature materials and systems.