Effect of temperature on corrosion behaviour of 15CrMo steel in saline (Na 2 siO 3 ) steam/water

Abstract

The experiments were performed to investigate the corrosion behavior of 15CrMo steel in the saline (Na₂SiO₃) water/steam. The samples was analysed using scanning electron microscopy/energy dispersive spectrum (SEM/EDS) and X-ray diffraction (XRD). The results indicate that the dissolved Na₂SiO₃ in the steam/liquid phase has obvious effects on the corrosion. In the steam phase, the main corrosion products are crystal NaFe(SiO₃) and Fe₃O₄. The stick-shaped microstructures (T = 280°C) are gradually converted to acicular-shaped microstructure (T = 320°C). The acicular structures connect with each other under higher temperature (T = 360°C). The relative contents of elemental Fe are 65.65%, 65.39% and 66.5% under the three temperatures, which present little changes. In the liquid phase, the main corrosion product in matrix phase is only NaFe(Si₂O₆) regardless of temperature. The surface is covered by scattered clusters with branches in radical pattern. The clusters accumulated gradually with temperature increasing. The relative content of elemental Fe decreases from 38.11% to 24.69%.