Study On Corrosion Of Rebar Embedded In Concrete By Wire-beam Electrode

The corrosion of rebar in concrete was studied by 8x8 liner wire-beam electrode. The corrosion potential, polarization resistance and corrosion rate distributions of iron wires electrode were obtained by estimated corrosion potential and polarization resistance when concretes were in different corrosion environments. The effects of [Cr]/[OH~] ratio, different mediums, crack, water liner and ethanolamine on concrete corrosion were studied. The polymers coating was obtained by spreading polyo-toluidine to epoxy. The anticorrosion mechanism of polyo-toluidine was studied by contrasted protection ability of epoxy coating with polyo-toluidine as a additive and epoxy coating when pH value were 2 and 7.The results showed that the wire beam electrode could be used to study non-uniform corrosion of rebar in concrete. The corrosion of iron wires in concrete was non-uniform. The corrosion potential and polarization resistance were scattered. With the increase of immersion time, the corrosion potential shifted negatively, the polarization resistance reduced and the difference of corrosion potential became larger. With increasing the embedded depth of iron wire, the negative shift value of corrosion potential, chlorine ion concentration and corrosion rates reduced, but polarization resistance increased. It could be concluded from the simulated pore solution study that the corrosion of iron wire was heavy with high Cl-concentration in same pH value condition, and it was also heavy with high pH value in same Cl- concentration condition.The corrosion potentials of iron wires in 10% NaCl solution and 10% MgSO4 solution shifted negatively with the immersion time, and they were scattered. The pH value of concrete in 10% MgSO4 solution reduced more than that in 10% NaCl solution. The corrosion of iron wires in NaCl solution was much heavier than in MgSO4 solution. It was basically the same of the iron wire corrosion tendency between in simulated pore solution and in concrete.The corrosion of iron wires in concrete with crack immersed in 10% NaCl solution was non-uniform. The Cl- and O2 concentrations at crack region were higher than uncracked regions, so the corrosion rate of iron wires at crack region was higher than uncracked regions at early-immersed stage. With continued immersed, the Cl- and O2 penetrated to uncracked regains and the penetration of O2 at cracked regain wasdifficult, so the degree of non-uniform corrosion significantly lowered. The non-uniform corrosion caused by crack could be weakened by ethanolamind penetrated to concrete and adsorb at the surface of iron wires.The corrosion of iron wires was non-uniform with concrete partly immersed in 10% NaCl solution. The key factors of iron wire corrosion were concrete resistance and penetration of O2.The epoxy with polyo-toluidine as an additive provided a better protection than epoxy coating when pH values were 2 and 7. The passivating oxide layer formed on steel provided by polyo-toluidine improved the protection ability. The passivating was not so considerable when pH value was 7. It was the epoxy that provided the most barrier protection.