Electrochemical Impedance Spectra for the Corrosion of Porous Cu-35mass%Ni-(5,10)mass%Cr Alloys in Molten(0.62Li,0.38K)_2CO_3 at 650 ℃ in Air

摘要

The electrochemical impedance spectra was employed to investigate corrosion behavior of porous Cu-35mass%Ni-5mass%Cr and Cu-35mass%Ni-10mass%Cr alloys in molten (0.62Li,0.38K)_2CO_3 at 650 ℃ in air. The results show that the Nyquist plots for the corrosion of two alloys are composed of two capacitive loops which indicate that localized corrosion occur for the total immersion time. The differential potential between Cu-rich phase and Cu-depleted phase contributes to galvanic corrosion of the alloys. As compared to porous Cu-35mass%Ni-5mass%Cr, porous Cu-35mass%Ni-10mass%Cr is more corrosion resistant, which is related with its smaller area fraction of the cathodic Cu-rich phase. In addition, crevice corrosion in the pores of the alloys promotes the micro-crack generation and expansion.