In this work, the corrosion behaviours of the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy and its crystalline counterpart are studied in acidic, neutral, and alkaline solutions by scanning electron microscopy, electrochemic...In this work, the corrosion behaviours of the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy and its crystalline counterpart are studied in acidic, neutral, and alkaline solutions by scanning electron microscopy, electrochemical impedance spectroscopy, and potentiodynamic and potentiostatic polarization tests. X-ray photoelectron spectroscopy and scanning Kelvin probe are employed to characterize the alloy surface. The results show that the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy presents a better corrosion resistance compared to its crystalline counterpart, which is attributed to the uniform energy distribution of the atoms on the amorphous alloy surface, and this presents as a uniform electric potential map to effectively suppress the occurrence of the corrosion cell reaction.展开更多
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 ...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 seawaterconcrete. Corrosion behavior was analyzed by electrochemical impedance spectroscopy. The composition and morphologyof corrosion products were characterized by X-ray diffraction, energy-dispersive spectrometry and scanning electronmicroscopy. Meanwhile, oxide film produced by preheating before spray coating was investigated by X-ray photoelectronspectroscopy and Mott-Schottky technology. Results indicated that corrosion behavior of ECR with pinhole defectexhibited three stages when immersed in the uncarbonated/carbonated SPS. In the initial stage, steel in defect waspassivated when exposed in the uncarbonated SPS and corroded when exposed in the carbonated SPS, due to competitiveadsorption between chloride and hydroxyl ions. In the second stage, the oxide film under coating reconstituted （thethickness and defects density decreasing） in the uncarbonated SPS, which was caused by the synergy between highhydroxide 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 corrosionoccurred under the coating around the pinhole in the uncarbonated SPS, which was probably induced by ion diffusion at thenano-scale coating/steel interface. The corrosion products adjacent to the defects were re-oxidized from FeCIa.4HaO andFe2（OH）3Cl to Fe2O3.H2O, and the corrosion area was expanded outward in the carbonated SPS.展开更多
文摘In this work, the corrosion behaviours of the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy and its crystalline counterpart are studied in acidic, neutral, and alkaline solutions by scanning electron microscopy, electrochemical impedance spectroscopy, and potentiodynamic and potentiostatic polarization tests. X-ray photoelectron spectroscopy and scanning Kelvin probe are employed to characterize the alloy surface. The results show that the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy presents a better corrosion resistance compared to its crystalline counterpart, which is attributed to the uniform energy distribution of the atoms on the amorphous alloy surface, and this presents as a uniform electric potential map to effectively suppress the occurrence of the corrosion cell reaction.
基金supported financially by the Strategic Precursor Research Program of the Chinese Academy of Sciences(No.XDA13040500)
文摘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 seawaterconcrete. Corrosion behavior was analyzed by electrochemical impedance spectroscopy. The composition and morphologyof corrosion products were characterized by X-ray diffraction, energy-dispersive spectrometry and scanning electronmicroscopy. Meanwhile, oxide film produced by preheating before spray coating was investigated by X-ray photoelectronspectroscopy and Mott-Schottky technology. Results indicated that corrosion behavior of ECR with pinhole defectexhibited three stages when immersed in the uncarbonated/carbonated SPS. In the initial stage, steel in defect waspassivated when exposed in the uncarbonated SPS and corroded when exposed in the carbonated SPS, due to competitiveadsorption between chloride and hydroxyl ions. In the second stage, the oxide film under coating reconstituted （thethickness and defects density decreasing） in the uncarbonated SPS, which was caused by the synergy between highhydroxide 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 corrosionoccurred under the coating around the pinhole in the uncarbonated SPS, which was probably induced by ion diffusion at thenano-scale coating/steel interface. The corrosion products adjacent to the defects were re-oxidized from FeCIa.4HaO andFe2（OH）3Cl to Fe2O3.H2O, and the corrosion area was expanded outward in the carbonated SPS.
