腐蚀产物MgO对Fe基合金在固态和熔融NaCl-MgCl2 中高温耐蚀性能的影响

Effects of Corrosion Product MgO on Corrosion Resistance of Fe-based Alloys in Solid and Molten NaCl-MgCl2 at High Temperature

摘要:

熔融氯化盐是下一代聚光式太阳能热发电站（第3代CSP）候选传热和储热介质，含MgCl₂的熔融氯化盐对金属传热管道和储热容器腐蚀后在其表面形成MgO，MgO对管道耐腐蚀性能影响尚不清楚。通过对比碳钢和3种Fe-Cr-Ni合金在固态（345 ℃）和熔融NaCl-MgCl₂（445和545 ℃）中的腐蚀行为，分析了MgO对4种试样在不同温度下的腐蚀行为机理。结果表明，在固态NaCl-MgCl₂中，碳钢表面MgO壳致密且连续，可以保护试样免受腐蚀。在熔融NaCl-MgCl₂中，4种试样表面也生成了致密的MgO壳，但它因热应力作用而开裂和剥落，熔融盐沿着氧化膜裂纹渗入MgO/基体界面，发生化学-电化学联合腐蚀反应，不能保护试样免受该熔盐腐蚀。

Abstract:

Molten chloride salt is a candidate heat transfer medium (HTM) for the next generation high temperature concentrating solar power (CSP). A corrosion product MgO will be formed on metal surface in the molten chloride containing MgCl₂. Based on the corrosion behavior comparison of a carbon steel and three kinds of Fe-Cr-Ni alloys in solid (345 °C) and molten state NaCl-MgCl₂ (445 and 545 °C), the effects of MgO on corrosion resistance of the four kinds of samples were discussed. Results show that in solid eutectic NaCl-MgCl₂ at 345 °C, the MgO layer is dense and complete on the carbon steel surface, which can protect the specimen from corrosion. In the molten salt, a dense MgO layer is also formed on the four kinds of sample surface, but the molten salt penetrates the MgO/matrix interface along cracks of the oxide layer due to the peeling off of MgO layer under thermal stress, which cannot protect specimen from corrosion. The corrosion mechanism is the chemical-electrochemistry reactions.