氯化鈉沉積量對耐熱鋼熱腐蝕之作用

The Effects of NaCl Deposits on the Hot Corrosion of Heat-resisting Steels

針對STP A24、STP A26、253MA、310SS及353MA五式合金，於850℃進行2~20mg/cm2 沉積量之氯化鈉熱腐蝕試驗。藉由金相觀察、腐蝕深度和定性及定量分析等方式，比較並瞭解氯化鈉之沈積量對腐蝕行為之影響。實驗結果顯示，鐵鉻系STP A24及STP A26之腐蝕形態僅為金屬損失，而鐵鉻鎳系之253MA、310SS及353MA除金屬損失外，另呈現內侵蝕之腐蝕形態。除STP A26外，其它四式合金之腐蝕量均隨氯化鈉之沈積量而增加。合金浸泡於熔融NaCl時，以溶解流失之方式造成金屬損失；各合金之主要組成元素中，以鉻具有最大之溶失傾向，以致310SS之金屬損失量高於STP A24與STP A26。

The purpose of this study is to investigate the NaCl-induced hot corrosion behavior of five commercial steels (containing STPA24, STPA26, 253MA, 310SS, and 353MA). The effects of NaCl deposits and environments on the hot corrosion of the steels were also evaluated by means of morphology observation, depth of attack, and quantitative analysis methods. The results showed that: The corrosion morphology of Fe-Cr base alloys (STPA24 and STPA26) show the metal loss only, however, the Fe-Cr-Ni base alloys (253MA, 310SS and 353MA) showed not only metal loss but with a subscale attack. Except STPA26, the corrosion of alloys increased with increasing the amounts of NaCl deposits. As alloys immerged in molten NaCl, the metal loss resulted from metal dissolving. Since Cr has the most tendency to cause the mental dissolving, the metal loss of 310SS which contains the highest amounts of Cr is more than those of STPA24 and STPA26.