This paper presents results from a series of experiments carried out in a H2-based gas mixture containing 24.4% CO and 2.4% H2O. Discontinuous tests have been carried out at 560°C for periods of up to 200 hours. This gas mixture has a carbon activity well above 1, placing it in a regime where the gas is considered to be super-saturated with carbon. As a result, carbon is precipitated from the gas phase and deposited onto metallic surfaces as graphite. In this way, these experiments simulate conditions found in petrochemical plants that have been shown to lead to a form of catastrophic attack, known as “metal dusting”. Several commercial candidate reformer tube materials have been exposed to the gas mixture at nominally 1.5 bar (absolute) in order to establish their relative performance under these conditions. An
additional material, a 12%Cr ferritic steel containing 2.75% Si has been exposed at the same time since the presence of silicon is known to improve carburisation resistance and its influence on metal dusting
has not been fully evaluated. Surface condition may also play a role and this has also been taken into consideration during this study.
Cross-sectional microstructural analyses are presented showing the nature and extent of attack and the underlying mechanisms responsible for this form of degradation are discussed in relation to the variables covered by this study. Kevwords: metal dusting, alloy steels, surface condition, Si-content, carbon-deposition.