The electrochemical behavior of corrosion and passivation for Q235 carbon steel in acidic phosphate buffer solutions without and with NO2−
Anti-Corrosion Methods and Materials
ISSN: 0003-5599
Article publication date: 4 August 2020
Issue publication date: 30 September 2020
Abstract
Purpose
The purpose of this paper is to reveal the mechanism of nitrite (NO2−) for the surface passivation of carbon steels in acidic environments through investigating the influences of 0.01 mol/L NaNO2 addition on the corrosion and passivation behaviors of Q235 carbon steel in acidic phosphate buffer (APB) solutions (pH 2 to 6).
Design/methodology/approach
The electrochemical techniques including open circle potential evolution, potentiodynamic polarization, electrochemical impedance spectroscopy and cyclic voltammetry were applied.
Findings
In APB solutions without NO2−, the Q235 steel presented the electrochemical behaviors of activation (A), activation-passivation-transpassivation and self-passivation-transpassivation at pH 2 to 4, pH 5 and pH 6, respectively; the corrosion rate decreased with the up of pH value, and the surface passivation occurred in the pH 5 and pH 6 solutions only: the anodic passivation at pH 5 and the spontaneous passivation at pH 6.
Originality/value
In APB solutions without NO2−, the corrosion rate decreased with the up of pH value, and the surface passivation occurred in the pH 5 and pH 6 solutions only: the anodic passivation at pH 5 and the spontaneous passivation at pH 6. With the addition of 0.01 mol/L NaNO2, into APB solutions, the variation of corrosion rate showed the same rule, but the surface passivation occurred over the whole acidic pH range, including the anodic passivation at pH 2 to 4 and the spontaneous passivation at pH 5 to 6.
Keywords
Acknowledgements
The work is supported by the National Natural Science Foundation of China (Contract 51601133), the Middle-aged and Young University Teachers’ Basic Ability Promotion Project of Guangxi (Contract 2019KY0612) and the Science Research Project of High Level Talents in Yulin Normal University (Contract G2019ZK53).
Citation
Hu, X., Zhang, P., Zhou, Y. and Yan, F. (2020), "The electrochemical behavior of corrosion and passivation for Q235 carbon steel in acidic phosphate buffer solutions without and with NO2−", Anti-Corrosion Methods and Materials, Vol. 67 No. 5, pp. 473-481. https://doi.org/10.1108/ACMM-03-2020-2285
Publisher
:Emerald Publishing Limited
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