SHI Zhou, WANG Chi, LI Ying-ming, ZHAO Xu-po, SHEN Rui-li, HUANG Li-ji, YAO Chao-yi
To study the corrosion evolution characteristics and corrosion resistance of the zinc based multi-element alloy anchoring system for bridge cables, based on copper salt ice acetate salt spray corrosion tests, combined with scanning electron microscope (SEM) microscopic morphology observation , energy dispersive spectroscopy (EDS) techniques and high resolution X-ray diffraction (XRD) corrosion product analysis, the corrosion macroscopic morphology, corrosion products, corrosion quality changing, corrosion microscopic morphology, and variation of the corrosion microcracks' number and width of the cable anchoring system specimens were studied. The Arrhenius equation was introduced to analyze the corrosion resistance. The results showed that at the interface between the anchor material and the steel wire, the corrosion distribution of the anchor body is radial with the steel wire as the center, and the corrosion of the anchor body is denser and faster near the steel wire, with flaky corrosion points appearing at 15 days, continuous corrosion points at 30 days, and the formation of corrosion pits at 60 days. The anchor material-anchorage interfaces are mainly uniformly corroded, and the accumulation of corrosion products in the gaps exacerbates the outer corrosion. The corrosion quality changing rate of ZnAl9Cu1MgRE alloy anchor specimens is lower than that of ZnAl6Cu1 alloy, the former has stronger corrosion resistance. Observation of surface microstructure (SEM) shows that the number of microcracks at the “anchor material-steel wire” interface and the “anchor material-anchorage” interface increases rapidly and then slows down with the corrosion process. The growth rate is the fastest at 15-60 days, and decreases after 60 days due to the widening and merging of microcracks. Energy dispersive spectroscopy (EDS) analysis shows that the corrosion morphology characteristics of the anchor material, anchorage surface, “anchor material-steel wire” interface, and “anchor material-anchorage” interface are basically the same. The corrosion mechanism is that Cl- pitting corrosion causes honeycomb like depressions, tumor like protrusions under the electric couple effect, volume expansion and ion diffusion interact to generate sheet-like stacking morphology, and hydrogen embrittlement and internal stress coupling promote microcracks. The X-ray diffraction (XRD) indicates that the main corrosion products on the surface of the anchor material are ZnO, Zn(OH)2, Cu6Al2 (OH)16CO3 et al. The main corrosion products of the anchorage are Fe3O4 and Fe5CuO8, and the corrosion of Zn is accelerated at the “anchor material-steel wire” and “anchor material-anchorage” interfaces due to electrode effects. Based on the Arrhenius equation calculation, the apparent activation energies of ZnAl9Cu1MgRE alloy and ZnAl6Cu1 alloy at the “anchor material-steel wire” interface are 114.32 and 89.37 kJ·mol-1, respectively, both of which meet the A-level high corrosion resistance standard, and the former has relatively better corrosion resistance.