日本金属学会誌

J. Japan Inst. Metals, Vol. 54, No. 4 (1990),
pp. 458-465

Hot Corrsion of Nickel under Cathodic Polarization in Molten Na2SO4

Motoi Hara1, Katsuji Takahara2 and Yutaka Shinata1

1Department of Metallic Engineering for Materials, Mining College, Akita University, Akita
2Graduate Student, Akita University, Akita. Present address: Fujikura Ltd., Tokyo

Abstract:

The hot corrosion behavior of nickel under cathodic polarization in molten Na2SO4 has been investigated by the measurement of corrosion loss, the observation of corrosion morphology and the analysis of corrosion product. Corrosion loss of nickel under cathodic polarization in molten Na2SO4 increased remarkably with an increase in the quantity of electricity for cathode reaction. On the contrary, the corrosion loss of nickel under cathodic polarization in molten NaCl was independent of the quantity of electricity for cathode reaction and was small. The feature of severe attack was observed for the surface of nickel after cathodic polarization in molten Na2SO4. A large amount of powdered corrosion product was detected in Na2SO4 melt after cathodic polarization. Such a corrosion product was found to consist of Ni and NiO from X-ray diffraction analysis. The cathodic polarization reaction and the reaction products were examined in order to discuss a mechanism for cathodic corrosion for nickel in molten Na2SO4. As a consequence, it was found that a two-electron reaction in which SO42- was a reactant occurred and O2- was produced by the reaction. It was considered on the basis of these facts that the corrosion of nickel under cathodic polarization in molten Na2SO4 proceeded mainly as an association of nickel with O2- and SO2 which were cathodic products.


(Received 1989/10/7)

Keywords:

hot corrosion, nickel, cathodic corrosion, molten salt, sodium sulfate


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