关键词: Fe基合金, 钝化膜, 电子性质, 点蚀敏感性

Abstract: The formation process of passive film on iron and electronic properties and pitting susceptibility of an iron-based alloy are investigated by using linear potential sweep, alternative current impedance and electrochemical nose technologies. The relationship between reciprocal square capacitance and potential following the Mott-Schottky behavior is limited at a narrow rang of low potentials. At higher potentials, linear relationship between reciprocal capacitance and potential is obtained, which is ascribed to the increasing thickness of the passive film with potential. The donor density of the passive film is influenced by the formation potential of the film, passivator and microstructure. The decrease in the formation potential of the passive film and the existence of reduced or deposited passivator can increase the donor density of the passive film and lead to low resistance to pitting corrosion. The high-to-low order of pitting susceptibility for the individual microstructure is ferrite> martensite>pearlite. There exists interaction between different microstructures with different donor density, which results in pitting initiation and propagation on the weak microstructure.

Key words: Iron-based alloy, Passive film, Electronic property, Pitting susceptibility