Influence Of Mo On Atmospheric Corrosion Of Q420 Weathering Bridge Steel

Weathering steel has been widely used in the field of bridge construction due to its excellent mechanical properties and corrosion resistance.However,compared with foreign countries,China still has a big gap in weathering steel,so it is necessary to further explore the field of weathering steel.In this dissertation,weathering steel plates with mass fractions of 0.05%,0.21% and 0.49% with different Mo contents were designed and prepared according to the standards of weathering steel for Q420 Bridges,and the indoor simulated dry-wet cycle accelerated corrosion experiment was carried out in industrial atmospheric environment and Marine atmospheric environment.The effect and mechanism of Mo on the corrosion performance of weathering steel were explored by observing the macroscopic morphology,electrochemical properties,phase composition,microcosmic morphology and element distribution of the surface of the rust layer.The corrosion rates of the three experimental steels in the two corrosion environments decreased with the increase of Mo content,and the corrosion resistance increased.With the increase of Mo content,the self-corrosion potential of the experimental steel increases in a positive direction,the slope of the anode line increases,the corrosion tendency of the experimental steel decreases,and the impedance of the rust layer increases and the conductivity decreases.In the composition of the rust layer,the proportion ofα-FeOOH beneficial to the stability of the rust layer increased,and the generation of loosely structured γ-FeOOH and β-FeOOH was inhibited.Defects such as cracks and holes in the cross section of the rust layer decrease with the increase of Mo content,and the thickness decreases.The position of Cl element in the rust layer also keeps away from the side of the matrix with the increase of Mo content.Similarly,Mo promotes the density of the rust layer.Compared with the role of Mo in the industrial atmospheric environment and the Marine atmospheric environment,in the electrochemical experiment,the rust-bearing steel in the industrial atmospheric environment increased with the increase of Mo content,and the anode line slope and impedance increased more.The proportion of α-FeOOH in therust layer increases more obviously with the increase of Mo content,while the proportion of α-FeOOH in the Marine atmospheric environment has little difference in the later corrosion stage of the three experimental steels.Therefore,Mo plays a more important role in improving the corrosion resistance of weathering steels in the industrial atmospheric environment.