ごみ焼却炉模擬環境における合金の耐食性評価への交流インピーダンス法の適用

抄録

Electrochemical impedance measurements of 31 alloys have been carried out in NaCl-KCl-Na₂SO₄-K₂SO₄-ZnSO₄ melts under air containing H₂O and HCl at 723, 773 and 873 K. Regarding relatively good corrosion resistant alloys, the interface of alloy/molten salt can be represented by an equivalent circuit model consisting of a charge transfer resistance, double layer capacitance solution resistance and finite diffusion impedance. Meanwhile, the impedance characteristics of poor corrosion resistant alloys can be explained by a transmission line equivalent circuit model in which the current distribution inside pores of thick porous oxide layers formed on the surface is considered. A good correlation was established between the reciprocal of impedance at 10 mHz and the corrosion rates calculated from mass loss after immersion tests. The AC impedance method was shown to be useful as rapid corrosion test for evaluating the corrosion performance of alloys in molten salt environments.