Immersion experiment was carried out to investigate the CO 2 corrosion behavior of low-alloy steel used for pipeline at vapor-saturated CO 2 and CO 2 -saturated brine conditions by revealing microstructure, corrosion rate, corrosion phases, surface/cross-section morphology, and elements distribution. The results demonstrate that mass losses at both conditions are approximately linear to corrosion time with log scale, and the corrosion rate at vaporsaturated CO 2 condition is greatly lower than that at CO 2 -saturated brine condition. The main corrosion phases consisting of inner layer and outer layer are Cr-rich compounds and FeCO 3 crystals, respectively. Corrosion products on the coupon surface produced at vapor-saturated CO 2 condition are formed locally, while the ones produced at CO 2 -saturated brine condition deposit on the coupons surface homogeneously. That distinction is caused by the difference of formation process of corrosive solution. According to the experimental results, corrosion mechanisms of low-alloy steel at both conditions are discussed to illustrate CO 2 corrosion behavior.

In this paper, immersion experiments were carried out to compare corrosion behaviors of low‐alloy steel exposed to both H2S/CO2 environments in terms of corrosion kinetics, corrosion products, macroscopic/microscopic surface morphology, cross‐section morphology, and elemental distribution. The experimental results demonstrated that the corrosion kinetics of both the corrosion environments was similar. The distinctive corrosion environment accelerated the formation of different corrosion products. The corrosion products of vapor‐saturated H2S/CO2 environment were mackinawite, cubic iron sulfide, and greigite, while, the ones of H2S/CO2‐saturated brine environment were mackinawite and cubic iron sulfide. The surface formation process was also similar. The vapor‐saturated H2S/CO2 environment promoted the formation of fine crystals compared with H2S/CO2‐saturated brine environment. Molybdenum accumulated in the inner layer in both the corrosion environments. Two schematic models of corrosion process are proposed based on the experimental data.

In this paper the smelting separation of high-alumina rich-manganese ore prepared with selective reduction and magnetic separation was proposed to produce the high carbon ferromanganese alloy (HCFeMn). The rational smelting separation parameters for high-alumina rich-manganese ore included the FC/O of 1.1, the smelting temperature of 1550°C, the smelting time of 60 min, and the basicity of 0.7. The smelting separation of high-alumina rich-manganese ore was achieved successfully. The content of Fe, C, Si and other impurities (P, S) were 12.13%, 6.73%, 0.17% and 0.14, 0.008, respectively. Especially, the recovery and the content of Mn reached 80.47% and 76.76%. The obtained high carbon ferromanganese alloy met the higher standard (FeMn78C8) of ferromanganese alloy, especially the content of Si P and S in the HCFeMn alloy was far below the standard value. Based on the SEM-EDS, XRD and thermodynamic calculation, the smelting and separation mechanisms of high-alumina rich-manganese ore was proposed to more effectively explain the effect of smelting parameters on slag/metal separation behaviors during the process of smelting HCFeMn alloys.