J. Mater. Sci. Technol. ›› 2016, Vol. 32 ›› Issue (4): 341-348.DOI: 10.1016/j.jmst.2015.11.015

• Orignal Article • Previous Articles     Next Articles

Effects of Cl- Ions on the Corrosion Behaviour of Low Alloy Steel in Deaerated Bicarbonate Solutions

Yunfei Lu1, 2, Junhua Dong1, *, Wei Ke1   

  1. 1 Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;
    2 Wuhan the Second Ship Design and Research Institute, Wuhan 430064, China
  • Received:2015-02-27 Revised:2015-06-17 Online:2016-04-10
  • Contact: Ph.D.; Tel.: +86 24 23915912; Fax: +86 24 23894149. (J. Dong).

Abstract: The effect of Cl- ions on corrosion evolution of NiCu low alloy steel during immersion tests (up to 70 days) in deaerated 0.05 mol/L bicarbonate solutions was investigated by in-situ electrochemical measurements combined with X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) characterisations. The results showed that due to the acceleration of substrate dissolution in the presence of Cl-, corrosion of NiCu low alloy steel underwent only two stages, i.e., a quick oxidation process followed by a final metastable passive state, without the initial slow anodic dissolution as observed in the Cl--free bicarbonate solution. The main components of the formed rust layer in the Cl--free bicarbonate solution were α-FeOOH and Fe3O4, while apart from α-FeOOH, Fe6(OH)12CO3 was found evident instead of Fe3O4 in the Cl--containing solution. Metastable pits were only found in the Cl--containing solution where Cl- accumulated after the immersion test, confirming the attack of Cl- on the substrate after penetrating the formed corrosion product layer.

Key words: Low alloy steel, Corrosion behaviour, Cl-, Open circuit potential, Electrochemical impedance spectroscopy (EIS)