鐵基合金於750℃氯化鈉／硫酸鈉混合鹽之熱腐蝕

The Hot Corrosion of Fe-based Alloys with pre-coating NaCl/NaSO4 Mixtures at 750℃

以STP A26及SS 310兩種商用高溫鋼材，探討噴覆沈積2mg/cm2不同混合比之NaCl/Na2SO4混合鹽，於750℃靜滯空氣中之高溫熱腐蝕行為。藉由熱重動力學、腐蝕形態、侵蝕深度、金屬損失以及X-ray定性分析之結果，解析熱腐蝕現象與其反應機制。研究結果顯示，此兩種合金於75wt%NaCl/25wt% Na2SO4之混合鹽沈積時，有最嚴重之侵蝕，且幾乎隨NaCl含量之增加，腐蝕愈嚴重。STP A26因氯氧化反應生成大量Fe2O3、Fe3O4生成物，以致基材表面被持續且直接侵蝕。而310耐熱鋼，則因無法生成緻密的Cr2O3保護性氧化皮膜，繼而又因皮膜的碎裂，使得基材大量鉻空乏，形成內侵蝕孔洞造成加速侵蝕。

The high-temperature corrosion behaviors of STP A26 and 310 commercial heat-resistant steels have been studied at 750℃ in air with 2 mg/cm2 mixtures of various NaCl/Na2SO4 ratios. The corrosion behaviors and mechanisms are developed by the weight gain kinetics, morphologies, depth of attack, metal loss and X-ray analysis. The results show that the most severe corrosion has been taken place at the 75/25 wt% NaCl/Na2S04 ratio for both alloys and increased with NaCl content in the mixtures. During the heating process at 750℃, the STP A26 has been formed non-protective oxides, such as Fe2O3 and Fe3O4, due to the oxychloridation reaction which the corrosive substances attack the substrate alloy directly and continuously. For the 310 heat-resistant steel at the same condition, the loose and cracking of the Cr2O3 protective oxide scale has the effect of the chromium consumption and results in the internal attack in the substrate seriously. The lost of the materials for the high temperature corrosion with the mixing of salts increased i.e. the corrosion attack is thus enhanced.