The Galvanic or Electromotive Series

Source M. /. Orion and R. O. Dean, Swimming Pool Corrosion , paper to San Francisco Bay Section of the National Association of Corrosion Engineers, October J963. 

The rate of corrosion (loss of metal) is proportional to the amount of current that flows in the corrosion cell. From Ohm s law we know that, for direct current, 

E potential difference, volts / = current, amperes R = resistance, ohms 

Reactions occurring during corrosion are conveniently divided into those taking place at the anode and those taking place at the cathode. The reactions may be (and usually are) more extensive and complex than the primary oxidation reduction half-reactions. Let us consider the corrosion of a piece of iron pipe. The basic galvanic cell is illustrated in Fig. 7-12. 

At anodic areas an oxidation reaction releases Fe ions into solution, leaves electrons behind in the metal, and produces a negative charge on the metal. 

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