The Research of Corrosion Mechanism of Galvanized Steel in Concrete

The corrosion behavior and resistance of hot-dip galvanized steel were studied in a saturated Ca(OH)2 aqueous solution containing chloride ions (Cl−) in concrete. In the saturated Ca(OH)2 aqueous solution, which simulated water in the concrete pores, Ca(Zn(OH)3)2·2H2O was formed on the surface of the hot-dip galvanized steel, acting as a protective film. However, the corrosion rate of zinc increased as the Cl− concentration increased. This is presumed to be owing to the formation of Zn5(OH)8Cl2·H2O and CaCO3 on the surface and the decrease in the coverage of the protective film Ca(Zn(OH)3)2·2H2O. However, in concrete, the corrosion of hot-dip galvanized steel was not promoted by the cyclic corrosion test. This may be because the Cl− that penetrated into the concrete did not reach the depth of the galvanized steel and the Ca(Zn(OH)3)2·2H2O that was formed during the curing of the concrete remained after the cyclic corrosion test.