Effect of W/C ratio and cover thickness on polarization characteristics of embedded steel in mortar

The effects of cover thickness and W/C (water-to-cement) ratio on polarization properties of embedded steel bar were investigated with electrochemical methods. Corrosion potentials shift to the noble direction with increasing the cover thickness. In addition, when the cover thickness increasingly becomes thinner and thinner, effect of the W/C ratio on variation of corrosion potential increases as well. Impedance value at 100 kHz indicating the resistance of cover thickness increases with the decrement of W/C ratio as well as the increment of cover thickness. However, in the case of W/C ratio at 0.6, impedance at 10 mHz shows the relatively larger value than that at W/C ratio of 0.4 or 0.5 in the range of cover thickness from 4 to 8 cm, which is probably expected that oxide film built up on the surface of steel bar due to strong alkali environment by hydration reaction with increasing W/C ratio is performed as the resistance polarization. It is also observed that liquid junction potential tends to increase with decreasing W/C ratio.