Polarization of the Galvanic Cell

The different phenomena of polarization of the anodic and cathodic reactions (activation, diffusion, convection) should be well known as a function of the evolution and change of the properties of the interface as a function of time. The polarization behavior of the cathode and anodic reactions on the two electrodes should be examined. In natural atmospheres, the cathodic reaction controls frequently the rate of attack. The diffusion of oxygen is an important parameter to avoid control and polarization of the corrosion by the rate of the cathodic reaction (8) (Fig. 1.8). 

The resistance overpotential of the cell IR is mainly a function of the conductivity of the electrolyte solution and the distance between the electrodes as the electrolytic resistance is more important than the electric resistance of the metals. Thus if dissimilar pipes are butt-welded with the flow of electrolyte, the most severe corrosion will occur near the weld on the active metal. In soft water, the critical distance between 

Volts versus saturated calomel reference electrode 

Stainless steel-types 316,3171 I I Nickel-copper alloys 400, K-500 

Silver Nickel 200 Silver-bronze alloys Nickel-chromium alloy 600 

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Figure 5.43. UP-spectra of Ag YSZ electrodes for (a) cathodic and (b) anodic polarization of the galvanic cell Ag YSZ Pd,PdO at 547°C. In (b), the shift of the Fermi edge of the small silver particles on YSZ under anodic polarization is shown enlarged (5x).24 Reprinted with permission from Wiley-VCH.

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