氧化皮膜種類對鐵基合金於900℃氯化鈉熱腐蝕之防蝕作用

The Performance of Oxide Scales on the Corrosion Resistance of Fe-based alloys in NaCl-Induced Hot Corrosion at 900℃

本研究針對低碳鋼、310不銹鋼及鐵–29錳–8.5鋁–2.2鉻–2.5矽–0.75碳等三式合金、於900 ℃靜態空氣氣氛進行1～144小時9mg/cm2氯化鈉之沉積熱腐蝕試驗。藉由金相觀察、侵蝕深度、熱重動力學資料、EPMA定性與定量分析及熱力學資料計算等方式，比較Cr2O3及Al2O3 生成合金於氯化鈉沈積之熱腐蝕特性。實驗結果顯示，低碳鋼之熱腐蝕最為嚴重，鐵錳鋁鉻矽碳合金由於生成之Al2O3氧平衡解離壓極低，故形成於合金/腐蝕產物之合金側、可有效隔離氯化鈉腐蝕鹽之作用，因此獲得最佳之抗熱腐蝕特性。而310不銹鋼則因氯化鉻之熱力學特性近似於氯化鐵、以致310不銹鋼之熱腐蝕特性與低碳鋼類似。

Low carbon steel, 310 stainless steel and Fe-29Mn-8Al-2.5Si-2Cr-0.74C alloy casting with initial 9mg/cm2 NaCl surface coating were oxidized at 900℃ in still air for 1~144 hr to investigate the hot corrosion resistance and behaviors of these alloys. In order to identify the corrosion characteristic of Cr2O3-and Al2O3-forming alloys, the OM examination, depth of attack, corrosion kinetics, EPMA analysis techniques and thermodynamic calculations were taken in this study . Because of the low dissociation pressure oxides formed near the alloy surface, which can prevent the chlorine to attack alloy. The results showed that the Fe-Mn-Al-C alloy displayed a better corrosion resistance than the other steels. The hot corrosion characteristic of 310 stainless steel is similar to low carbon steel, due to the thermodynamic properties of chromium-chlorides are resembling to the iron chlorides.