Effect of Microstructure and Cr Content in Steel on CO2 Corrosion

Abstract

Abstract The effect of microstructure and Cr content in steels on CO2 corrosion was investigated by using steels containing Cr content from 0 to 13 mass% melted in laboratory and Steels J55, N80 and L80(API Grade) melted in the mill. Temperatures and H2S contamination were considered as environmental factor. In CO2 environments, the temperature giving a maximum corrosion rate, Tmax. existed in carbon and Cr steels. Tmax. increased together with Cr content, and Tmax. of 0, 1, 2 and 13% Cr steels was about 80, 100, 120 and 225°C, respectively. Because of this behavior, the relationship between Cr content and corrosion rate was linear at 60°C, but the corrosion rate was highest on the steel with around 1mass% Cr at 100°C. H2S contamination for CO2 corrosion suppressed the corrosion rate and localized-corrosion in the temperature region whose corrosion rate showed a maximum value. It was clarified that this was related to the formation of Fe-sulfides from EPMA analysis and the solubility of the corrosion products. Concerning microstructure, Steel J55 with ferritic-pearlitic microstructure showed good corrosion resistance for localized-corrosion compared with Steel N80 and L80 with martensitic microstructure.