Methods to Quantify Reactive Chromium Vaporization from Solid Oxide Fuel Cell Interconnects

C Key,J Froitzheim,P Gannon,R Smith,J Eziashi,R Amendola

doi:10.1149/2.0041409jes

Abstract

High-temperature (>600°C) reactive vaporization of Cr from chromia and stainless steels in oxidizing environments is an industrially relevant phenomenon that has been and will continue to be studied extensively for decades. Recently, many experimental techniques have been developed to measure Cr vaporization from stainless steel interconnect (IC) components within solid oxide fuel cell (SOFC) systems. Many of these techniques are based on an experimental method known as the transpiration method, which is used to generate Cr vapors and subsequently collect them for quantitative analysis. However, vapor collection and analysis methods differ significantly between investigators within the community, as does the array of alloys (with and without protective surface coatings), temperatures, flow rates, and water vapor pressures used in experimentation. Therefore, the purpose of the present work is to provide an overview of experimental techniques used to quantify reactive Cr vaporization, and to compare data reported in literature on Cr vaporization from Cr2O3 and chromium containing alloys in oxidizing environments.

Highlights

Hexavalent Cr is a well-known carcinogen,[26] especially in the gaseous phase
The Knudsen effusion method has been used extensively to study thermodynamic properties of vapors and solids in equilibrium, yet is only applicable when vapor pressures are less than 1 Pa (10−5 atm).[27,28]
The method has been used since the mid-1800s to study vapor pressures, dissociation pressures, gas/solid and gas/liquid equilibria from a wide variety of material systems,[25] and is ideal for measurements performed at atmospheric pressure with small concentrations of Cr vapors in the reactant gas

Summary

Introduction

Hexavalent Cr is a well-known carcinogen,[26] especially in the gaseous phase. Investigators should be prudent with exhausted vapors and avoid contact with Cr(VI) in the condensed phase.The transpiration method.— There are many ways to study high temperature vaporization processes. The Knudsen effusion method has been used extensively to study thermodynamic properties of vapors and solids in equilibrium, yet is only applicable when vapor pressures are less than 1 Pa (10−5 atm).[27,28] Vapors at higher pressures can be measured through static pressure measurements, but are of limited use when multiple gas species are present For this reason, the transpiration method, known as the transportation or entrainment method, has become one of the most popular ways to study Cr vaporization from SOFC-ICs.[4,13,14,16,22] The method has been used since the mid-1800s to study vapor pressures, dissociation pressures, gas/solid and gas/liquid equilibria from a wide variety of material systems,[25] and is ideal for measurements performed at atmospheric pressure with small concentrations of Cr vapors in the reactant gas

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Methods

Conclusion