Elsevier

Corrosion Science

Volume 39, Issue 3, March 1997, Pages 589-603
Corrosion Science

The effect of molybdenum on the stability of passive films formed on amorphous Fe-Cr-Mo-P-C alloys by potentiostatic polarization in deaerated 1 M HCl

https://doi.org/10.1016/S0010-938X(96)00148-5Get rights and content

Abstract

Open circuit immersion immediately after potentiostatic polarization is carried out to investigate the effect of molybdenum addition on the stability of the passive films formed on amorphous Fe-8Cr-13P-7C alloys by polarization in de-aerated 1 M HCl at −100 mV(SCE), which is in the passive region of both chromium and molybdenum. The open circuit potentials of both molybdenum-free and -containing alloys decrease with immersion time after polarization, apart from the passive potential region of chromium but in the passive region of molybdenum. The passive film formed on molybdenum-free alloy by polarization for 10 min and 2.5 h is disrupted by open circuit immersion for 30 min, and the alloy was corroded seriously, whereas molybdenum-containing alloys passivated by polarization for 10 min remains in the passive state during subsequent immersion for 5 h. Regardless of polarization time and molybdenum addition, the cationic fraction of chromium in the surface film decreases continuously with immersion. Open circuit immersion leads to an increase in the concentration of molybdenum ion in the film on the alloys polarized previously for 10 min and a remarkable enrichment of molybdenum ion occurs after prolonged immersion, showing the formation and stabilization of molybdenum-enriched passive film. On the other hand, the enrichment of molybdenum ion during immersion is more difficult in the film on the alloys polarized previously for 2.5 h than that on the alloys polarized previously for 10 min.

References (27)

  • K. Asami et al.

    Corros. Sci.

    (1978)
  • H. Habazaki et al.

    Mater. Sci and Engng.

    (1991)
  • M.-W. Tan et al.

    Corros. Sci.

    (1995)
  • M.-W. Tan et al.

    Corros. Sci.

    (1996)
  • M.-W. Tan et al.

    Corros. Sci.

    (1996)
  • K. Sugimoto et al.

    Corros. Sci.

    (1977)
  • R. Goetz et al.

    Electrochim. Acta

    (1982)
  • K. Hashimoto et al.

    Corros. Sci.

    (1979)
  • M.-W. Tan et al.

    Corros. Sci.

    (1995)
  • K. Asami

    J. Electron Spectrosc.

    (1976)
  • K. Asami et al.

    Corros. Sci.

    (1977)
  • K.S. Kim et al.

    J. Electron Spectrosc.

    (1974)
  • K. Asami et al.

    Corros. Sci.

    (1977)
  • Cited by (11)

    • Fe-based metallic glass composite coatings by HVOF spraying: Influence of Mo on phase evolution, wear and corrosion resistance

      2022, Materials Characterization
      Citation Excerpt :

      It must be pointed out here that the difference in icorr is insignificant compared to one order of magnitude difference in ipass values of P1C and P2C coatings, revealing better passivation ability of P2C. Whereas, the spontaneous passivation in P2C coating can be attributed to the rapid evolution of protective film due to hindered dissolution of Cr during passivation by formation of Mo-oxide film in potential region for active dissolution of Cr, thereby facilitating formation of passive Cr-rich film [58,59]. Moreover, the values of all the corrosion properties in terms of noblest Ecorr, lowest icorr, highest Epit and lowest ipass also substantiate the superior corrosion resistance of P2C.

    • Effects of Cr and Mo additions on formation and mechanical properties of Arc-sprayed FeBSiNb-based glassy coatings

      2018, Journal of Non-Crystalline Solids
      Citation Excerpt :

      The relationship between Cr concentration and corrosion resistance has been well established in Fe-based amorphous metals, where Cr increases the chemical potential for electrochemical corrosion on the one hand, and promotes the formation of a stable and compact passive chromium oxide (or/and oxyhydroxide) film on the other [33]. Moreover, the minor addition of Mo facilitates the formation of the passive chromium oxyhydroxide by the formation of passive tetravalent molybdenum oxide film in the potential regions where Cr actively dissolves [34]. And it suppresses the active dissolution of Cr in these potential ranges.

    • Laser assisted Fe-based bulk amorphous coating: Thermal effects and corrosion

      2014, Journal of Alloys and Compounds
      Citation Excerpt :

      In addition, high concentrations of Mo develop a trivalent Molybdenum oxide and prevent the dissolution of chromium from the chromium oxide passive layer. Thus, greater concentration of Mo results in spontaneous passivation [34,44–46]. Furthermore, it has been reported that carburization of steel improves the corrosion resistance [43] and in the present case, the absence of martensitic phase further confirms the super saturation of solute element (carbon) that is likely to drastically reduce the Ms (martensitic start) temperature and thus avoiding martensitic phase formation.

    • Anomalous corrosion resistance behavior of Mo-containing SS in alkaline media: The role of microstructure

      2011, Materials Chemistry and Physics
      Citation Excerpt :

      This development is mostly due to economic reasons inasmuch as the role of Mo is still not fully understood. This lack of scientific knowledge concerning the role of Mo can be illustrated by a fundamental disagreement in the literature as to whether Mo is a component of passive films [3,4] or not [5–7]. The consequences of a more widespread use of these alloys are difficult to predict.

    View all citing articles on Scopus
    View full text