CO₂ corrosion resistance of low-alloy steel tempered at different temperatures

The microstructure and corrosion resistance in a CO2-saturated salt solution have been examined for a low-alloy steel subjected to different tempering treatments. It is found that corrosion resistance increases with increasing tempering temperature from 300°C to 600°C. Tempering at the different temperatures affects the formation of the corrosion scale. Comparing different samples after corrosion tests, iron oxy-hydroxide chloride is found to be more prevalent in the sample tempered at 600°C. This sample also demonstrates delayed development of a semi-protective iron carbonate layer. Cementite produced by high-temperature tempering enables increased retention of Fe2+ ions and thus restoration of dissolved scale.