纯Cr和两种含Cr合金在ZnCl_2及KCl-ZnCl_2盐膜下的腐蚀

CORROSION BEHAVIOR OF PURE Cr AND TWO Cr-CONTAINING ALLOYS BENEATH ZnCl_2 AND KCl-ZnCl_2 DEPOSITS

研究了纯Cr、低合金钢及HP型耐热钢在 45 0℃纯氧气氛中分别于ZnCl2 和KCl-ZnCl2 盐膜下的腐蚀 .结果表明 ,材料在混合盐膜下比在单一ZnCl2 盐膜下发生了更严重的腐蚀 .与低合金钢相比 ,纯Cr和耐热合金中的腐蚀产物更为疏松并易剥落 .此外 ,HP耐热合金中还沿富Cr碳化物发生了晶间侵蚀 .从热力学角度讨论了形成Cr2 O3型保护膜的材料在含氯环境中的蜕化机理 .

The corrosion behavior of pure Cr,one low alloy steel and an HP-type heat-resistant steel were studied in the presence of ZnCl 2 and KCl-ZnCl 2 deposits respectively in oxidizing gaseous environments at 450℃.All materials suffered from seriously accelerated corrosion beneath mixture salts than in single ZnCl 2 deposit.The oxide scales formed on pure Cr and heat-resistant steel were easily to spall and had even worse adherence to the matrix compared with that on low alloy steel,whereas the latter had a higher mass gain during corrosion.Furthermore,Cr-rich Cr 7C 3 carbides were attacked preferentially induced by chlorine in comparison to the matrix of the heat resistant steel.The results show that the Cr-containing alloys do not exhibit excellent corrosion resistance to this chlorine-contaminant environment due to the poor adherence of the scales to the matrix.The accelerated corrosion mechanism for those Cr 2O 3-forming materials is discussed thermodynamically.