NiCr合金在KCl-ZnCl_2盐膜下含氯氧化性气氛中的腐蚀

Corrosion of NiCr alloys in oxidizing atmosphere containing HCl induced by KCl-ZnCl_2 salt deposit

研究了纯Ni、纯Cr以及3种不同Cr含量的NiCr合金在600℃KCl-ZnCl2盐膜下含氯氧化性气氛中的腐蚀行为.结果表明,5种材料均发生了严重的加速腐蚀.在材料表面形成了多孔的氧化膜,并发生了开裂,在氧化膜与基体金属的界面处有金属氯化物生成.NiCr合金的腐蚀增质比纯Ni和纯Cr的小.Ni50Cr和纯Cr有较高的腐蚀速度,前者与其具有的双相组织有关,后者是其氧化膜易脱落所致.材料的加速腐蚀机制是氯化物蒸汽的气相输运加速了金属离子向外扩散速度的‘活化氧化’.

The corrosion of pure nickel and chromium and of three NiCr alloys containing 10%, 25% and 50% Cr in a HCl-containing oxidizing atmosphere with KCl-ZnCl2 deposit at 600°C was investigated. All the materials suffer from accelerated corrosion with respect to their corrosion in the same atmosphere in the absence of chloride deposit. In particular, both metals corroded more quickly than the three NiCr alloys especially during the initial stage. The scales formed on the five materials were very porous with cracks and composed of oxides or/and chlorides of both metals as well as some Cr-Zn/K spinel. Moreover, the chlorides of both metals were found at the metal- or alloy-scale interface. Finally, the corrosion mechanism was discussed in terms of accelerated oxidation induced by chlorides.