Abstract
The stress corrosion cracking is the central issue for high-strength wires under high tensile stress used in civil engineering. This paper explores the resistance of stress corrosion cracking of three typical steel wires of high-strength carbon through a laboratory test, combining the actions of tensile stress and corrosive solution. Besides, the impact of tensile stress and immersion time are also investigated. During the tests, the wires were subject to electrochemical measurements of potentiodynamic polarization and electrochemical impedance spectroscopy, and the microstructure analysis was performed on the fractured cross sections. The obtained results show the following: the high-strength wire, conforming to GB/T 5224, has higher resistance to the combined actions of tensile stress and corrosive solution; tensile stress of 70% fracture strength and longer loading-immersion time make the film of corrosion products on steel surface unstable and weaken the corrosion resistance; the surface film consisted of the iron oxide film and the corrosion products film whose components are mainly iron thiocyanate and iron sulphide.
Highlights
Due to the high bearing capacity and stiffness, the prestressed concrete (PC) structures are widely used in large-span building, bridge and hydraulic structures [1]
By comparing the Nyquist curves of stressed wires (A, B, C under 70% f t ) and stress free wire (A, 0% f t ), it was found that the capacitance arc magnitude of stress free wire A is much larger than the wires (A, B, C) under 70% f t tensile stress, indicating that the tensile stress promotes substantially the occurrence of corrosion
Rsol represents the resistance of the solution, the constant phase angle element CPE1 corresponds to the stressed wires (A, B, C under 70% ft) and stress free wire (A, 0% ft), it was found that the capacitance double-layer capacitance of the interface between the sample surface and solution, R1 represented the arc magnitude of stress free wire A is much larger than the wires (A, B, C) under 70% ft tensile stress, charge transfer resistance, R2 was the surface film resistance, the constant phase angle element CPE2 indicating that the tensile stress promotes substantially the occurrence of corrosion
Summary
Due to the high bearing capacity and stiffness, the prestressed concrete (PC) structures are widely used in large-span building, bridge and hydraulic structures [1]. Walter [9] reported 242 cases of prestress failure, from 1951 to 1979, among which a large portion were attributed to the environmental actions Among these failure causes, the stress corrosion cracking (SCC) is always a main engineering concern as it reduces the fracture strength of high-strength steel wires, leading to unexpected brittle failures of PC structures [10,11]. It is of interest to compare the SCC performance for streel wires with similar chemical compositions from different standards To this purpose, this study retains three steel wires, conforming to BS 5896 [21] and GB/T 5224 [22], and investigates the SCC resistance of these wires through stress-immersion tests and the role of stress on the electrochemical behaviors
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