Passivation process of X80 pipeline steel in bicarbonate solutions

• Published in: International journal of minerals, metallurgy and materials Vol. 18; no. 2; pp. 178 - 184
• Main Authors: Zhou, Jian-long, Li, Xiao-gang, Du, Cui-wei, Pan, Ying, Li, Tao, Liu, Qian
• Format: Journal Article
• Language: English
• Published: Beijing University of Science and Technology Beijing 01.04.2011; Springer Nature B.V
• Subjects: Anodic; Bicarbonates; Capacitance; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Corrosion and Coatings; Electrochemical impedance spectroscopy; Electrochemistry; Electrode polarization; Equivalent circuits; Glass; High strength low alloy steels; Impedance; Materials Science; Metallic Materials; N-type semiconductors; Natural Materials; Nyquist plots; Nyquist图; Passivation; Passivity; Pipelines; Steel; Steels; Structural steels; Surfaces and Interfaces; Thin Films; Tribology; X80管线钢; 浓度范围; 电化学阻抗谱; 电容测量; 碳酸氢; 钝化工艺; passivation; bicarbonate solutions; potentiodynamic polarization k[electrochemical impedance spectroscopy; pipeline steel
• ISSN: 1674-4799; 1869-103X
• DOI: 10.1007/s12613-011-0419-8

The passivation process of X80 pipeline steel in bicarbonate solutions was investigated using potentiodynamic, dynamic electro-chemical impedance spectroscopy （DEIS）, and Mott-Schottky measurements. The results show that the shape of polarization curves changes with concentration. The critical ＇passive＇ concentration is 0.009 mol/L for X80 pipeline steel in bicarbonate solutions. No anodic current peak exists in solutions when the concentration is lower than 0.009 mol/L, whereas there are one and two anodic current peaks when the concentration ranges from 0.009 to 0.05 mol/L and is higher than 0.1 mol/L, respectively. DEIS measurements show that there exist active dissolution range, transition range, pre-passive range, passive layer formation range, passive range, and trans-passive range for X80 pipeline steel in the 0.1 mol/L solutions. The results of DEIS measurements are in complete agreement with the potentiodynamic diagram. An equivalent circuit containing three sub-layers is used to explain the Nyquist plots in the passive range. Analyses are well made for explaining the corresponding fitted capacitance and impedance. The Mott-Schottky plots show that the passive film of X80 pipeline steel is an n-type semiconductor, and capacitance measurements are in good accordance with the results of DEIS experiment.