N6 和 Monel400 镍合金在中国南海深海环境下的腐蚀行为研究

通过实海暴露实验，研究了N6纯Ni和Monel400镍合金在中国南海海域800和1200 m深海环境下的长周期 (3 a) 腐蚀行为。采用SEM，EDS和XRD技术，分别进行了腐蚀形貌观察，腐蚀产物成分和相组成分析。结果表明：在深海环境下，Monel400镍合金的耐局部腐蚀能力要优于N6纯Ni。N6纯Ni在绿色腐蚀产物膜 (由NiCl₂6H₂O组成，还覆盖有少量的CaCO₃和MgCO₃等无机盐类) 下发生了很严重的隧道腐蚀，甚至出现了局部穿孔现象。Monel400镍合金表面生成了宽浅型的点蚀坑，点蚀坑上覆盖有由 (CuNi)₂Cl(OH)₃组成的腐蚀产物。N6纯Ni和Monel400镍合金的最大点蚀坑深度均随水深的增加而降低。

Corrosion Behavior of N6 and Monel400 Nickel Alloy in Deep Sea Environment of South China Sea

The corrosion behavior of N6 nickel and Monel400 nickel alloy in 800 and 1200 m deep sea environment of South China Sea was studied by field test. The morphology and composition of corrosion product were examined by means of SEM, EDS and XRD techniques. The results indicated that the resistance to localized corrosion of Monel400 nickel alloy was better than that of N6 nickel. The green corrosion product of N6 nickel was composed of NiCl₂6H₂O with a small amount of CaCO₃ and MgCO₃, under which severe tunnel corrosion occurred, while localized corrosion induced perforation even took place on N6 nickel samples. However, shallow and large size corrosion pits formed on Monel400 nickel alloy, which were covered by green corrosion product consisted of (CuNi)₂Cl(OH)₃. Comparing with the data of literatures, the maximum pit depth of N6 and Monel400 nickel alloy decreased as the depth of test side increased.