高溫配管用鉻鉬鋼於水蒸汽氣氛之氯化鈉熱腐蝕

The Hot Corrosion Behavior of Cr-Mo Steels with NaCl Deposits in Humidity Atmospheres

針對STPA 24、STPA 26二式合金，於450℃、600℃及750℃噴覆2mg/cm2氯化鈉之0% H2O、10% H2O、50% H2O流動氣氛，探討腐蝕氣氛源及水蒸汽之作用。在含水蒸汽的氣氛中，合金之腐蝕以解離機構進行，不易形成保護性之Cr2O3，腐蝕皮膜生成二層以上之多孔質組織，其氧化物成長為柱狀，當柱狀氧化物與上層氧化物連結時，增加金屬離子之固體擴散路徑，且由於氫運載氧氣向內擴散，導致腐蝕速率增加。

The purpose of this study is to investigate the effects of humidity on the high temperature corrosion behavior of Cr-Mo alloy steels (STP A24 and STP A26). The experiments were performed at 450, 600, and 750℃ in 0%, 10%, and 50% humidity on specimens with 2mg/cm2 NaCl deposits. In atmospheres containing humidity, the dissociation mechanism of corrosion suppresses the formation of protective Cr2O3 but forms a bilayer porous scale. The corrosion rates increased by the solid diffusion of cations and the inward diffusion of hydrogen through the columnar oxide that grew form the alloy substrate to the outer scale.