Research On The Influence Of Microstructure And Alloy Elements On The Corrosion Resistance Of Rebar

In recent years,with the rapid development of the construction of cross sea bridge?Cross Harbour Tunnel?harbor engineering and ocean engineering,more and more infrastructure need to be constructed in the marine environment,however,the commen rebar in the market now cannot meet the corrosion resistance requirements.In this case,the corrosion resistant rebar has a good application prospect in the marine environment for its good corrosion resistance and low cost.The immersion experiment was conducted in the atmosphere simulated the marine environment to research the variation of corrosion rate of the different microstructure and alloy elementsaddition rebar with time;the evolution of the phase composition with time and the rust layer of the rebar were analyzed by the scanning electron microscope?optical microscope and XRD method;the mechanism of the corrosion resistance rebar is discussed by the potentiodynamic polarization curve and impedance.Conclusions are as follows:The corrosion potential of F+B rebar is higher than that of F+P rebar with the same composition in the marine environment,simulated by using 3.5%NaC l solution.And the average corrosion rate of F+B rebar was significantly lower than that of F+P rebar;The stability time of F+B rebar is in foront of F+P rebar in the medium term and the average corrosion rate of the two rebar become similar in the later.The results show that the influence of the microstructure on the corrosion resistance of the two kinds of rebar was only stay before the formation of stable rust layer.The polarization curves of the rebar with higher alloy elements of Cr and Mn appear unstable passivation film and the addition of Cr and Mn in the rebar could also enhance the pitting corrosion.Causing the initial average corrosion rate was significantly higher than the rebar with low addition of Cr and Mn,long-term impedance values was significantly larger and the relative corrosion rate decreased significantly.the average corrosion rate of t he higher Cr(1.26%)added rebar in the whole corrosion period was significantly lower than that of low Cr addition(0.04%)rebar,high content of element Cr can make the Self-corrosion current of the matrix significantly lower and passivation apper obviously.In the eraly stage,The average corrosion rate of rebar is flat,and the average corrosion rate of the matrix was reduced by the enrichment of chromium and oxygen which can form compounds in the cracks and holes.The trend of average corrosion rate decreased later.During the corrosion process,no obvious enrichment of element Mn was found,which indicated that the effect of element Mn on the corrosion rate was not significant in 3.5%NaCl solution.During the experience,the thickness of the rust layer of the rebar increased gradually with the extension of corrosion cycle,and the rust layer phase was composed of Fe3O4,?–FeOOH and?–FeOOH,also a small amount of NaC l have invaded in the early stage of the corrosion.It play an important role in reducing the later average corrosion rate that the cottony ?–FeOOH phase emerged in the later of the corrosion.The category of microstructure and the content of alloy elements are both have influence on the phase change in the rust layer,the corrosion resistance of the rebar can be artificial enhanceed by improving the microstructure and controlling the content of the added alloy elements.