The influence of carbonaceous surface impurities on excrescence initiation in the rimming steel/CO2/CO system

The influence of surface carbon contamination in determining the sites of excrescence growth has been studied, for the reaction of rimming steel in carbon dioxide containing 1·5%CO + 1000 ppm H₂O + 10 ppm CH₄ at 17·25 × 10⁶ N m^?2 and 450°C. Patterns visible in the oxide layer in the early stages of oxidation can be attributed to hydrocarbon impurities remaining on surfaces not rigorously cleaned. The impurity can accumulate at specific areas on the surface and can then accelerate oxidation such that excrescences start growing early in the normally protective stage. Surface cleaning procedures and their limitations for corrosion studies are discussed.