Corrosion Electrochemical Characteristics of the Passive Films Formed on Inconel 718 Alloy in the Environments Containing High H_(2)S and CO_(2) Partial Pressures

摘要

The Electrochemical Impedance Spectroscopy (EIS), Mott-Schottky (M-S) curves and Polarization curves of the passive films formed on Inconel 718 alloy exposed in different corrosion environments containing H_(2)S and CO_(2) were investigated. The EIS results show that the passive film resistance reduced and the passive film capacitance increased gradually as the corrosion environments turned rigorous, which means that the negative ion absorbed on the surface reacted with the metal cation quickly. The reaction will lead to the dissolution of passive film formed on Inconel 718 in the environments containing H_(2)S and CO_(2) quickly. The M-S curves results show that the acceptor concentration in the passive films increased with the corrosion rigorous. The polarization curves results show that the electrode reaction rates are different in different corrosion environments. When the electric potential scanned from 0 V to the positive voltage, the passive films formed on the surface of Inconel 718 dissolved and the base metal near the film changed to passive films gradually. As a result, the passive films formed in the high acidic environments turn thinner for the reason of the dissolution rate of film faster than that of formation rate.