Effect Of Si Cotent On Atmospheric Corrosion Resistance Of Q420qENH Steel

Weathering steel has excellent corrosion resistance and used in Bridges widely.It is of great significance to study corrosion resistance mechanism of regulating alloy elements to reduce the social loss that caused by weathering steel corrosion.At present,there is a lack of study on the influence of Si alloy element content on the corrosion of weathering steel under the National standard system.In order to ensure the welding and mechanical properties of weathering steel,Q420qENH steel was used as the research material.The influence of Si alloy elements on the corrosion resistance was studied by regulated the composition content.In this paper,weathering steel with different Si element contents?0.12%,0.34%,0.48%?was designed as the research target.The corrosion process of weathering bridge steel was simulated by accelerating the simulation of coastal atmospheric environment and industrial atmospheric environment in the laboratory,and combined with exposure corrosion test.To study corrosion mechanism the paper was studied from the perspective of kinetics through corrosion weight gain.To explore the growth law of corrosion products and the effect of changes in the content of Si elements in weathering steel on the corrosion process,the paper was discussed by means of XRD,SEM,EDS,XPS and EIS experiments.The study show that the corrosion rate decreased with the extension of corrosion time,and the corrosion rate of weathering steel decreased with the increase of Si element content.The corrosion rate was the lowest when the content is 0.48%.In the process of corrosion product formation,the crystalline products formed by the rust layer mainly included?-FeOOH,?-FeOOH,?-FeOOH,Fe₃O₄,and the Si alloy elements in the weathering steel promoted the conversion of?-FeOOH and?-FeOOH to stable phase and?-FeOOH.With the extension of corrosion time,the rust layer gradually thickened and repaired the cracks that generated in the early stage.During the corrosion process,Si elements in the steel matrix separated out as ionic state,which affected the anode reaction in the electrochemical corrosion process.Si alloy element increased the self-corrosion potential of the corrosion products and reduce the anode corrosion current density.A certain amount of Si elements in weathering steel is conducive to reducing the growth of cracks and the formation of pores,promoting the compactness of corrosion products,and increasing the resistance of rust layer.The weathering steel with certain Si can effectively prevent the invasion of erosion ions,increase the physical and chemical barriers of weathering steel,and improve the corrosion resistance of weathering steel.