Cations effect on the passive film for carbon steels in concrete simulated pore solutions

• Published in: Journal of Building Engineering Vol. 94; p. 109945
• Main Authors: Wang, Xiaoxian, Yu, Xiaohan, Jin, Ming, Zhou, Yichuan, Liu, Jiaping
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2024
• Subjects: Carbon steel; Cation ions; Multi-scale measurements; Passive film; pH 12.5; Cation ions; pH 12.5; Carbon steel; Passive film; Multi-scale measurements
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2024.109945

The composition of the passive film on the carbon steel surface is a key step for understanding the protective properties of the carbon steel in concrete environment. Since the different cation ions lead the different protective properties, the impacts of different cation ions (Ca2+ and Na+) exposed in simulated pore solutions on the passive film formation at the passivation stage are investigated by electrochemical measurements and surface analysis methods. To reveal the main reasons for the protective properties of the passive film and clarify the evolution for the formation of the passive film under different cation ions. Electrochemical measurements show that most part of the passive film has already formed in the initial 72 h in an NH solution, whereas 168h is needed to form most of the passive in a CH solution. In addition, 216 h is enough to form a completed passive film during the natural passivation period. Surface analysis methods elucidate the passive film formed in a CH solution has more protective properties than that in an NH solution because more iron oxides are produced. Furthermore, the presence of Ca2+ ions in the pore solution significantly improves the protective properties of the passive film. •Determine properties of passive films by muti-scale methods.•Confirm Ca2+ plays a positive role in passive films.•Summarize the evolution of the passive film.