Corrosion Behavior of Epoxy-Coated Rebar with Pinhole Defect in Seawater Concrete
来源期刊：Acta Metallurgica Sinica2018年第11期
论文作者：Yao-Zong Mao Ying-Hua Wei Hong-Tao Zhao Chen-Xi Lv Hai-Jiao Cao Jing Li
文章页码：1171 - 1182
摘 要：Experiments were carried out to investigate the corrosion behavior of epoxy-coated rebar（ECR） with pinhole defect（diameter in hundreds of microns） immersed in the uncarbonated/carbonated simulated pore solution（SPS） of seawater concrete. Corrosion behavior was analyzed by electrochemical impedance spectroscopy. The composition and morphology of corrosion products were characterized by X-ray diffraction, energy-dispersive spectrometry and scanning electron microscopy. Meanwhile, oxide film produced by preheating before spray coating was investigated by X-ray photoelectron spectroscopy and Mott–Schottky technology. Results indicated that corrosion behavior of ECR with pinhole defect exhibited three stages when immersed in the uncarbonated/carbonated SPS. In the initial stage, steel in defect was passivated when exposed in the uncarbonated SPS and corroded when exposed in the carbonated SPS, due to competitive adsorption between chloride and hydroxyl ions. In the second stage, the oxide film under coating reconstituted（the thickness and defects density decreasing） in the uncarbonated SPS, which was caused by the synergy between high hydroxide and chloride activity, while in the carbonated SPS, crevice corrosion happened under the coating around pinhole,because of the different oxygen concentrations cell at the coating/steel interface. In the third stage, localized corrosion occurred under the coating around the pinhole in the uncarbonated SPS, which was probably induced by ion diffusion at the nano-scale coating/steel interface. The corrosion products adjacent to the defects were re-oxidized from FeCl2·4H2O and Fe2（OH）3Cl to Fe2O3·H2O, and the corrosion area was expanded outward in the carbonated SPS.
Yao-Zong Mao1,2，Ying-Hua Wei2，Hong-Tao Zhao2，Chen-Xi Lv2，Hai-Jiao Cao2，Jing Li2
1. School of Materials Science and Engineering, University of Science and Technology of China2. Institute of Metal Research, Chinese Academy of Sciences
摘 要：Experiments were carried out to investigate the corrosion behavior of epoxy-coated rebar（ECR） with pinhole defect（diameter in hundreds of microns） immersed in the uncarbonated/carbonated simulated pore solution（SPS） of seawater concrete. Corrosion behavior was analyzed by electrochemical impedance spectroscopy. The composition and morphology of corrosion products were characterized by X-ray diffraction, energy-dispersive spectrometry and scanning electron microscopy. Meanwhile, oxide film produced by preheating before spray coating was investigated by X-ray photoelectron spectroscopy and Mott–Schottky technology. Results indicated that corrosion behavior of ECR with pinhole defect exhibited three stages when immersed in the uncarbonated/carbonated SPS. In the initial stage, steel in defect was passivated when exposed in the uncarbonated SPS and corroded when exposed in the carbonated SPS, due to competitive adsorption between chloride and hydroxyl ions. In the second stage, the oxide film under coating reconstituted（the thickness and defects density decreasing） in the uncarbonated SPS, which was caused by the synergy between high hydroxide and chloride activity, while in the carbonated SPS, crevice corrosion happened under the coating around pinhole,because of the different oxygen concentrations cell at the coating/steel interface. In the third stage, localized corrosion occurred under the coating around the pinhole in the uncarbonated SPS, which was probably induced by ion diffusion at the nano-scale coating/steel interface. The corrosion products adjacent to the defects were re-oxidized from FeCl2·4H2O and Fe2（OH）3Cl to Fe2O3·H2O, and the corrosion area was expanded outward in the carbonated SPS.
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