Zairyo-to-Kankyo, 49, 684-689 (2000)
Difference in Corrosion Behavior of Pure Iron and Carbon Steel
in Short-time Exposure Test
Hideki Katayama*, Kazuhiko Noda*, Masahiro Yamamoto* and Toshiaki Kodama*
* National Research Institute for Metals (NRIM)
Corrosion behavior of pure iron and carbon steel in short-time exposure test was examined in detail by
electrochemical methods. Though the corrosion resistant of pure iron was better than that of carbon steel
in the initial stage of exposure test, the amount of corrosion losses for pure iron was more than that for
carbon steel after 6 month-exposure test. From the results of ESCA analysis and various electrochemical
measurements, it was found that the oxide film formed on pure iron in the initial stage of exposure test was
more stable and difficult to be attacked by chloride ions than that formed on carbon steel. On the other hand,
after 6 month-exposure test, it was indicated that the amount of ƒÁ-FeOOH that was reduced to magnetite
easily was abounding in the rust of the pure iron in comparison with that of the carbon steel.
Key words: atmospheric corrosion behavior, pure iron, carbon steel, exposure test, oxide film, rust
Vol.49, No.11 685
Table. 1 Chemical composition of the specimens . (mass%)
Fig. 1 Optical micrographs of cross section of pure iron (a) Fig. 2 Surface appearances of pure iron (a) and carbon steel
and carbon steel (b). (b) exposed at Tsukuba for 1 month.
686 Zairyo -to-Kankyo
Fig. 3 Amount of corrosion loss at Tsukuba and Choshi
after 6 month-exposure test.
Fig. 4 Anodic polarization curves of pure iron in borate
solution, which were measured after reduction at -
1.5V for 30 minutes and after formation of oxide film
in the desiccator.
Fig. 5 Anodic polarization curves of carbon steel in borate
solution, which were measured after reduction at -
1.5V for 30 minutes and after formation of oxide film
in the desiccator.
Fig. 6 ESCA spectra (O1S) of oxide films formed on surface
of pure iron and carbon steel before electrochemical
measurements.
Fig. 7 Anodic polarization curves of pure iron and carbon
steel in borate solution containing sodium chloride,
which were measured after preservation in desiccator
for 72 hours.
Fig. 8 Optical micrographs of surface of pure iron (a) and
carbon steel (b) after anodic chronoamperometry
measurement.
688 Zairyo-to-Kankyo
Fig. 10 Chronopotentiograms for pure iron and carbon steel
after 6 month-exposure at Choshi in Na2SO4.
[Boshoku Gijutsu (Corros. Eng.)], 17,
[Boshoku Gijutsu (Corros. Eng.)],
Vol.49, No.11 689
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