铝硅涂层在1050℃下含氯硫酸盐中的热腐蚀行为

Hot corrosion behaviour of Al-Si coating in chlorinated sulphate at 1050 ℃

采用涂盐法研究了铝硅涂层在1050℃下含氯硫酸盐（75%Na2SO4＋25%NaCl）中的热腐蚀行为,并与其在相同温度下混合硫酸盐中的热腐蚀行为进行对比,同时讨论了其热腐蚀机理。结果表明：铝硅涂层在1050℃下含氯硫酸盐中的热腐蚀较其在混合硫酸盐中更加严重;其在整个热腐蚀的过程中,不仅没能形成致密的保护性氧化膜,而且还发生了熔盐对涂层表面直接的化学腐蚀;此外,在热腐蚀前60 h涂层的质量一直在减小。分析认为,含氯硫酸盐中氯离子的存在,不仅加速了氧化铝膜的溶解进而诱发了化学腐蚀,而且所生成的氯气与Al反应生成挥发性的AlClx,造成了涂层在含氯硫酸盐中热腐蚀行为既不符合一般的氧化腐蚀规律,也不同于其在混合硫酸盐中的热腐蚀行为。

Hot corrosion behaviour of Al-Si coating in chlorinated sulphate（75% Na2SO4＋25% NaCl） at 1050 ℃ was studied by a coated-salt method, and compared with that in mixed sulphate at the same temperature. Moreover, the hot corrosion mechanism was also discussed. The results show that the hot corrosion of the Al-Si coating in the chlorinated sulphate is more serious than that in the mixed sulphate at 1050 ℃, and during the whole process of hot corrosion, it can not form a dense protective oxide film, moreover, direct chemical corrosion of molten salt on the surface of the coating occurrs. In addition, the mass of the coating decreases gradually during hot corrosion for 0-60 h. It is concluded that the presence of Cl^- in the chlorinated sulfate not only accelerates the dissolution of Al2O3 scale and induces chemical corrosion, but also the generated Cl2 gas reacts with Al to form volatile AlClx, resulting in the hot corrosion behavior of the coating in chlorinated sulfate is not in consistent with the general oxidation corrosion law, nor is it different from the hot corrosion behavior in mixed sulfate.