Study On The Structure And Corrosion Resistance Of Oxide Scale Of Rebar

Hot-rolled rebar,as a common steel in the construction industry,was widely used in industrial and civil buildings.Since the transportation and stacking of rebar were exposed to atmospheric environment,it often caused different degrees of corrosion on the surface,which reduced the product quality and performance of the rebar.The formation of oxide scale on the surface of rebar isolated the direct contact between the matrix and the air,and played a protective role.Therefore,it is of great significance to study the morphology and structure of oxide scale for improving the corrosion resistance of rebar in atmospheric environment.After rolling,the HRB 400 hot-rolled rebar under four different conditions of cooling bed temperatures were studied for its corrosion resistance in the same indoor and outdoor environment.The thickness,morphology and structure of oxide scale on the surface of rebar at different temperatures were measured by means of optical microscopy,scanning electron microscopy and electron backscatter diffraction technology.In order to obtained a suitable production process,we analyzed the influence of the cooling bed temperatures on the formation and corrosion resistance of oxide scale.The results showed that:?1?In the indoor environment,the surface of rebar is almost unchanged after being placed for a long time.And in the salt spray test,the corrosion rate of rebar is improved obviously with the increase of the cooling bed temperatures at prophase,the later is equivalent.In the outdoor environment,the corrosion resistance of rebar is improved with the increase of cooling bed temperatures.?2?The matrix microstructures of rebar are both F+P with different cooling bed temperatures.The thickness of the oxide scale increases with the improve of the cooling bed temperatures.The thinnest at 820?,the average thickness is only 24.13 um,and reaches 35.63 um at 1000?,both the integrity and continuity are improved.?3?The structure of oxide scale on the surface is basically composed of FeO and Fe₃O₄,outer layer Fe₃O₄,inner layer FeO.And the ratio of FeO and Fe₃O₄ content varies with the different cooling bed temperatures.The oxide scale is relatively dense with the increase of the cooling bed temperature.In order to improve the corrosion resistance of rebar in the atmospheric environment,the cooling bed temperatures should be appropriately increased to about1000?to ensure the integrity and compactness of the oxide scale,so as to improve the appearance quality and performance of the products.