Research On Electrochemical Corrosion Behavior Of Zn-5%Al Reinforced Rebar

Reinforced concrete is one of the most widely used as architecture materials in the twentieth century. However, the corrosion of rebar embed in the concrete is the researchers’ long-term concern. The two main reasons for the corrosion of reinforced concrete are carbonation and erosion of chloride ions. In this paper, the electrochemical corrosion behavior of Zn-5%Al reinforced concrete was studied, and the corrosion behavior of Zn-5%Al rebar in different environments, such as saturated Ca(OH)2 solution and concrete, were investigate, and the possibility of this Zn-5%Al coating applied in the rebar was discussed.This experiment was investigated by tafel polarization test and electrochemical impedance. The corrosion resistance of Zn-5%Al coating which immersed in the saturated Ca(OH)2 solution for different time was studied,and the resistance to chloride ions of sample with the corrosion product protection layer was discussed. The results showed that the corrosion current density of Zn-5%Al coating immersed for 15 days was 1.16×10-7A /cm2, it was close to the threshold value of 1.00×10-7A /cm2, the result of SEM and EDS showed that the corrosion products were dense Ca HZn with loose Ca HAl on it; When the concentration of the chloride ions is 0.1mol/L in the saturated solution, the results of 30days’ immersion experiment showed that the corrosion current density of the sample with corrosion product protection layer was 4.53×10-7A /cm2, when the chloride ions is 1mol/L, the corrosion current density of the sample with the corrosion product protection layer was 3.37×10-6A /cm2, it was showed that the corrosion resistance of the sample with corrosion product protection layer was decreased with the increase of chloride ions and the chloride threshold of the sample with corrosion product protection layer is 0.2mol/L.The electrochemical corrosion behavior of the Zn-5%Al reinforced concrete was investigated by wet and dry cycles accelerated test and galvanostatic accelerated corrosion test with EIS. The results of wet and dry cycles accelerated test showed that the resistance of concrete cover was decreased, firstly, and then it changed a little. The charge transfer resistance of ordinary rebar and Zn-5%Al rebar were decreased with the time increasing.Compared with the ordinary rebar, the corrosion resistance of Zn-5%Al reinforced concrete is better; The results of galvanostatic accelerated corrosion test showed that the resistance of concrete cover was increased firstly, and then it changed a little, the resistance of corrosion product layer and the charge transfer resistance of Zn-5%Al were decreased with the time increasing, and then it changed a little. When the galvanostatic accelerated corrosion test was applied to study the corrosion resistance of Zn-5%Al reinforced concrete, the results are much different from the corrosion behavior of reinforced concrete in the natural environment, while the results of the wet and dry cycles accelerated test have a high reference value.In conclusion, the corrosion resistance of Zn-5%Al reinforced concrete is better than the ordinary reinforced concrete, but not as good as hot dip galvanized rebar.