低合金鋼矽含量對其在重油燃燒廢氣中之高溫腐蝕的影響

Effect of Silicon Content in a Low Alloy Steel on its High Temperature Corrosion Resistance in Flue Gas of Heavy Oil

本研究是在實驗室建立重油燃燒廢氣在250-500℃之模擬氣氛，以比較不同矽含量之低合金鋼的腐蝕量，並在現場做試驗。結果顯示含0.46 wt%Si的鋼材比含0.21wt%Si者具較佳之抗蝕性。500℃下。腐蝕生成物之X光繞射分析和EPMA分析顯示抗蝕機構是Si比Fe優先氧化，產生含Si氧化鐵於銹皮和底材界面，阻止鐵離子或氧離子擴散，而前者鋼材之含Si氧化鐵比後者更厚，增加離子受阻礙之路徑，腐蝕速率因而降低。

This work is to develop a simulated flue gas of combustion heavy oil in laboratory, and to investigate the effect of silicon content in a low alloy steel on the corrosion at 250 - 500°C. Field test was also done. The result indicates that the steel with 0.46 wt% Si possesses better corrosion resistance than that with 0.21 wt% Si. X-ray diffraction and EPMA studies reveal that the corrosion resistant mechanism is due to the preferential oxidation of Si over Fe. Iron oxide rich in Si is produced at the scale/base metal interface and retards further diffusion of iron ions or oxygen ions. Furthermore, the Si rich-iron oxide of the former steel is thicker than that of the latter steel and may promote the path of the retardation of ions. The corrosion rate is thus reduced.