Corrosion Behavior of 20G Steel in Saline (Na2SO4) Circumstances at High Temperature/Pressure

Abstract To study the corrosion characteristic of 20G steel in saline circumstances with sodium sulfate (Na2SO4), a series of corrosion experiments are implemented on a novel setup. The corroded steel samples are analyzed by XPS and XRD. The results indicate that the effect of salinity on corrosion products in the gas phase is greater than that in the liquid phase. FeOOH is easier to form in the liquid phase than in the gas phase. The salinity of steam could promote the generation of Fe2O3. The relative content of Fe2O3 within the corrosion products that contained Fe in gas/liquid phase increases from 49.68%/36.30% (Na2SO4 concentration in solution, c = 0) to 95.70%/74.55%, separately (c = 4 g L−1). The salinity has an inhibiting effect on the generation of FeOOH. In the deionized water, the relative contents of FeOOH within the corrosion products that contained Fe are 36.01% (gas phase) and 56.43% (liquid phase), respectively. FeOOH hardly occurs as c = 4 g L−1. For corroded surface in Na2SO4 deposit, the main compositions detected are iron oxides (Fe2O3 and Fe3O4) and iron (Fe).