X-ray diffraction, Raman spectroscopy and scanning electron microscopy were employed to investigate the effects of the DC electric field on the composition, formation and structure of corrosion products formed on the surface of the steel immersed in NaCl solution. The results show that goethite(α-FeOOH), akaganeite(β-FeOOH), lepidocrocite(γ-FeOOH) and magnetite(Fe_3O_4) are the major constituents among the corrosion products. The arrangement of different levels of the DC electric field intensity gives rise to the following results. The little higher DC electric field intensity(around 100–200 k V/m) promotes the crystallinity and growth of γ-FeOOH; obviously, much higher DC electric field intensity(greater than 400 k V/m) prevents the growth of α-FeOOH and facilitates the generation of Fe_3O_4. Both the promotional growth of γ-FeOOH and suppression of a-FeOOH growth indicated the weakness of the protectiveness of the rust layer. Consequently, the suppression of the transformation of a-FeOOH from γ-FeOOH favors the yield of the Fe_3O_4,which works as a large cathode area and would be about to quicken the subsequent steel corrosion.
