Fireside Corrosion Behaviors of Super304H and HR3C in Coal Ash/Gas Environment with Different SO₂ Contents at 650 °C

The corrosion behaviors of Super304H and HR3C used for USC boiler applications were investigated in simulated coal ash/gas environments with 0.1 and 1.5% of SO₂ at 650 °C for 500 h. The results indicated that the increase in SO₂ accelerated the corrosion rate and the spalling tendency of the corrosion layer in both tested alloys. Fe₂O₃, Cr₂O₃ and FeCr₂O₄ main peaks were revealed by XRD on Super304H, but on HR3C only the Cr₂O₃ peak showed a high intensity. The SO₂ content did not affect the corrosion product composition of any of the alloys, but accelerated the inner sulfidation and the spallation on Super304H. No obvious internal sulfidation was observed on HR3C in either SO₂ content. Based on the experimental results, the alloy corrosion mechanism and the influence of sulfur content on the corrosion process were discussed.