Abstract

In this paper, the influence of semi-permeable film stabilisation on the corrosion trend, corrosion type and corrosion mechanism of bridge weathering steel in a deicing salt medium was investigated by dry and wet alternating accelerated corrosion test. The results indicate that the semi-permeable film stabilisation treatment reduces the inflection point of corrosion rate reduction of weathering steel plates and welded specimens in the deicing salt medium, reduces the value of n, which represents the trend of full-scale corrosion, and improves their resistance to full-scale corrosion. After 30 days of corrosion, the peak intensity ratios of Iβ-FeOOH+FeOCl /Iα-FeOOH for untreated plates and welded specimens were 1.092 and 1.132 times higher than that of the semi-permeable film stabilisation treatment specimens, respectively. With a reduction of defects and an increase in densification in the rust layer, and a significant reduction in the concentration of chloride ions at the interface between the rust layer and the substrate. During the whole corrosion process, the self-corrosion potential of the rust layer after the stabilisation treatment of the semi-permeable film was increased by 1.08–1.12 times, the impedance was increased by 1.13–1.32 times, and the electrochemical stability was significantly improved. The semi-permeable film in the pre-corrosion period effectively blocked the penetration of chloride ions, reducing the concentration of corrosion medium in the rust layer, reduced the generation of unstable phases of β-FeOOH and FeOCl. At the same time, the stabiliser treatment improves the Cu, Cr and Ni elements in the rust layer, promoted the formation of the stable phase α-FeOOH in the rust layer and the refinement of the rust grains, thus significantly improving the corrosion resistance of the weathering steel in the deicing salt medium.

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