碳钢和铁-铬-镍基合金合在相变储能材料熔融共晶氯化钠和氯化镁中腐蚀行为研究

Corrosion Behavior of a Carbon Steel and Iron-Chromium-Nickel Alloys in Molten Eutectic Sodium Chloride and Magnesium Chloride as Phase Change Material

摘要:

熔融氯化钠和氯化镁(NaCl-52 wt% MgCl2)作为中高温太阳能相变储热介质，对金属容器和管道具有很强的腐蚀性，其腐蚀机理也尚待深入研究。本文研究了三种铁-铬-镍基合金(Fe-Cr-Ni)和一种碳钢试样在520℃熔融共晶NaCl-MgCl2盐中的腐蚀行为。结果表明，碳钢试样境界处Fe原子优先变为亚铁离子(Fe2+)和铁离子 (Fe3+)，发生了严重的沿晶腐蚀，但表面形成了厚而致密的MgO壳，对试样起到了一定保护作用。三种Fe-Cr-Ni基试样表面也形成了MgO壳，但因铬元素优先被腐蚀，试样表面形成了疏松的富Ni骨架状微观组织结构，MgO壳或颗粒极易剥落，未能起到有效保护作用；Cr含量越高，腐蚀越严重。在太能能储能技术中，在廉价的铁基合金中添加镍元素，作为熔融氯化盐相变储热介质的容器或者管道材料，具有良好发展前景。

Abstract:

As a phase change material for solar energy storage at moderate- high temperature, the molten eutectic chloride salt of a sodium chloride and a magnesium chloride (NaCl-52 wt% MgCl2) is strongly corrosive to metal container and pipes. The corrosion behavior of three kinds of iron-chromium-nickel (Fe-Cr-Ni) alloys and a carbon steel in the molten eutectic salt at 520℃ were studied. Results show that the carbon steel is corroded along grain boundary for a iron atom become ferrous ion (Fe2+) and ferric ion (Fe3+). A thick and compact magnesium oxide (MgO) shell is formed on the carbon steel surface, which protects the specimen from corrosion. The MgO shell also formed on the three kinds of iron-chromium-nickel alloy surface, but the magnesium oxide shell can’t protect them from corrosion in the molten salt. Because a loose skeletal microstructure rich Ni is formed on specimen surface for the chromium element is preferentially corroded. The magnesium oxide (MgO) shell or particles peel off easily. In addition, the higher of the content of the chromium, the more serious of the corrosion As a vessel or pipe material for solar energy storage by molten chloride salt, a cheap iron-based alloy with alloy element nickel is more development prospects.