New Interpretation of the Effect of Hydrogen on the Ion Distributions and Structure of Passive Films on Microalloyed Steel

It has been reported that hydrogen decreases the stability of the passive films on iron and stainless steel and promotes their localized corrosion. However, the mechanism of hydrogen-promoted corrosion is still not clear. Potentiostatic, electrical impedance spectroscopy measurements, and Mott-Schottky analysis were used to investigate the effect of hydrogen on the properties of the passive film on X70 microalloyed steel. In the range of passive potentials, hydrogen retards the passive film formation and decreases its stability. Impedance spectra of passive film on X70 steel show that hydrogen decreases the resistance towards charge transfer and ion diffusion and increases the capacitance of the passive film. Mott-Schottky analyses show that hydrogen increases the capacitance and donor density, and decreases the flatband potential and the space-charge layer thickness of the passive film. A new explanation is proposed for the effects of hydrogen on the properties of the passive films. According to this explanation, hydrogen creates an additional electric repulsion on Fe 2+ or Fe 3+ and oxygen vacancies, and enhances the diffusion rate of cations and anion vacancies. At steady state, hydrogen will not only decrease the concentrations of O 2- and Fe 3+ , but also increase the concentration of Fe 2+ in the passive films, resulting in changes in the structure and a decrease in the thickness of the passive films.

[1]  Jingli Luo,et al.  Investigation of the Effect of Hydrogen on the Passive Film on Iron by Surface Analysis Techniques , 2003 .

[2]  D. Macdonald.  Passivity–the key to our metals-based civilization , 1999 .

[3]  Jingli Luo,et al.  Effects of Hydrogen on Semiconductivity of Passive Films and Corrosion Behavior of 310 Stainless Steel , 1999 .

[4]  D. Macdonald,et al.  On the Kinetics of Growth of Anodic Oxide Films , 1998 .

[5]  N. Sato.  CHAPTER 10 – SEMICONDUCTOR PHOTOELECTRODES , 1998 .

[6]  E. B. Castro.  Analysis of the impedance response of passive iron , 1994 .

[7]  D. Macdonald.  The Point Defect Model for the Passive State , 1992 .

[8]  R. A. Oriani,et al.  The role of hydrogen in the pitting of passivating films on pure iron , 1992 .

[9]  E. Mccafferty.  A Competitive Adsorption Model for the Inhibition of Crevice Corrosion and Pitting , 1990 .

[10]  R. A. Oriani,et al.  Hydrogen Permeation Through the Passivation Film on Iron by Time‐Lag Method , 1990 .

[11]  H. Pickering.  A Review of the Mechanism and Kinetics of Electrochemical Hydrogen Entry and Degradation of Metallic Systems , 1990 .

[12]  R. Kirchheim.  The growth kinetics of passive films and the role of defects , 1989 .

[13]  H. Pickering.  The significance of the local electrode potential within pits, crevices and cracks , 1988 .

[14]  R. Kirchheim.  Growth kinetics of passive films , 1987 .

[15]  U. Stimming.  Photoelectrochemical studies of passive films , 1986 .

[16]  R. A. Oriani,et al.  Hydrogen degradation of ferrous alloys , 1985 .

[17]  G. Horowitz.  Capacitance-voltage measurements and flat-band potential determination on Zr-doped α-Fe2O3 single-crystal electrodes , 1983 .

[18]  U. Stimming.  PROPERTIES OF THE PASSIVE FILM ON IRON ELECTRODES BY CAPACITY AND PHOTOCURRENT MEASUREMENTS , 1983 .

[19]  B. Conway,et al.  On the form of adsorption isotherms for substitutional adsorption of molecules of different sizes , 1973 .

[20]  C. D. Beachem,et al.  A new model for hydrogen-assisted cracking (hydrogen “embrittlement”) , 1972 .

[21]  F. Mazza,et al.  Chemical etching and pitting ofstainless steel , 1970 .

[22]  T. Noda,et al.  Single layer of the passive film on Fe , 1970 .

[23]  H. Engell,et al.  Untersuchungen über den Lochfraß an passiven austenitischen Chrom-Nickel-Stählen in neutralen Chloridlösungen , 1969 .

[24]  N. Sato,et al.  The Kinetics of Anodic Oxidation of Iron in Neutral Solution I . Steady Growth Region , 1964 .