Of Fe, Cr, Ni And Their Oxides In The Nacl, Kcl Molten Salt Corrosion Mechanism

Incineration has been adopted an effective and hygienic method for disposal of ever-increasing voluminous industrial and municipal solid waste in many countries including China. Some high calorific value section of it while utilizing waste as much as possible, generates heat, electricity and so on. In most cases, the corrosion problems in incineration environment are rather severe due to the complex reactions between the combustion gases containing chlorine or sulfur and salt deposits of chlorides and sulfates, in these environments metallic materials usually undergo an aggressive corrosion and degrade completely before the end of the designed life. The electrolytic deposits (ash or ionic salts) react with normally protective oxide films on alloy and give way to an accelerated corrosion attack known as hot corrosion. Considering the molten salt corrosion, it is very important to know the solubility of several oxides in the molten salt because this reveals the stability of the protective oxide films formed on metals in a molten salt corrosion environment.Solubility measurements of Fe2O3, Cr2O3 and NiO in molten NaCl and KC1 have been conducted in three different levels of basicity in order to elucidate the corrosion mechanism of materials in waste incineration environment and to develop highly corrosion resistant materials. The dissolution behavior of the oxides shows almost the same tendency as that shown by the dissolution behavior of the oxides in molten Na2SO4,NaCl-KCl and NaCl-KCl-Na2SO4-K2SO4 in literature. In a waste incineration environment, a protective Cr2O3 film easily dissolves in molten chlorides as CrO42- because pO2- of the molten chlorides tends to have deferent value due to the effect such as water vapor contained in the combustion gas.In this paper, the corrosion behaviors of pure Fe, Cr and Ni have been investigated in basic and mediun molten KC1. Fe,Cr,Ni corrod rapidly in medium molten KC1 and formed blistered, cracked and non-protective oxide scales. The Cr does not exhibit better corrosion-resistance and the corrosion rate is even higher than Ni. Due to a protective Cr2O3 film easily dissolves in the molten chlorides as CrO42-, the corrosion resistance of NiO was better than that of Cr2O3 . The weight losses of Fe,Cr,Ni in basic molten KC1 are less than those in medium molten KC1 and Ni exhibits better corrosion-resistance. After the initial stages of experiment, the weight loss of Ni isn't obvious and the tendency of it becomes gentler. The oxide scales of Fe, Cr, Ni become much thinner and possesses better adherence with the matrix. So we can hold the idea that we can reduce the dissolution behavior of oxide scales through changing the basicity in order to improve the corrosion-resistance of the materials. What's more, it shows that Ni is fitter for...