Relationship between the specific surface area of rust and the electrochemical behavior of rusted steel in a wet–dry acid corrosion environment

• Published in: International journal of minerals, metallurgy and materials Vol. 24; no. 1; pp. 55 - 63
• Main Authors: Liu, Wei, Zhao, Qing-he, Li, Shuan-zhu
• Format: Journal Article
• Language: English
• Published: Beijing University of Science and Technology Beijing 2017; Springer Nature B.V; Corrosion and Protection Center, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China
• Subjects: Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Corrosion; Corrosion and Coatings; Corrosion currents; Current density; Diffusion layers; Drying; Electrochemical analysis; Electrochemistry; Glass; Materials Science; Metallic Materials; Natural Materials; Relative humidity; Rusting; Specific surface; Steel; Surface area; Surfaces and Interfaces; Thin Films; Tribology; steel corrosion; specific surface area; electrochemical behavior; rust; polarization curves
• ISSN: 1674-4799; 1869-103X
• DOI: 10.1007/s12613-017-1378-5

The relationship between the specific surface area（SSA） of rust and the electrochemical behavior of rusted steel under wet–dry acid corrosion conditions was investigated. The results showed that the corrosion current density first increased and then decreased with increasing SSA of the rust during the corrosion process. The structure of the rust changed from single-layer to double-layer, and the γ-FeOOH content decreased in the inner layer of the rust with increasing corrosion time; by contrast, the γ-FeOOH content in the outer layer was constant. When the SSA of the rust was lower than the critical SSA corresponding to the relative humidity during the drying period, condensed water in the micropores of the rust could evaporate, which prompted the diffusion of O2 into the rust and the following formation process of γ-FeOOH, leading to an increase of corrosion current density with increasing corrosion time. However, when the SSA of the rust reached or exceeded the critical SSA, condensate water in the micro-pores of the inner layer of the rust could not evaporate which inhibited the diffusion of O2 and decreased the γ-FeOOH content in the inner rust, leading to a decrease of corrosion current density with increasing corrosion time.