CORROSION THEORYDOE-HDBK-1015/1-93CorrosionCH-02Rev. 0Page 4TABLE 1Electromotive - Force Series (77?F)ElementElectrodeStandard ElectrodeReactionPotential, v SodiumNa Na + e-2.712+MagnesiumMg Mg + 2e-2.34++BerylliumBe Be + 2e-1.70++AluminumAl Al+ 3e-1.67+++ManganeseMn Mn + 2e-1.05++ZincZn Zn + 2e-0.762++ChromiumCr Cr+ 3e-0.71+++IronFe Fe+ 3e-0.44+++CadmiumCd Cd + 2e-0.402++CobaltCo Co + 2e-0.277++NickelNi Ni + 2e-2.250++TinSn Sn + 2e-0.136++LeadPb Pb + 2e-0.126++HydrogenH 2H + 2e0.000 (reference)+CopperCu Cu + 2e+0.345++CopperCu Cu + e+0.522+SilverAg Ag + e+0.800+PlatinumPt Pt + 2e+1.2++GoldAu Au+ 3e+1.42+++The surface of any metal is a composite of a very large number of micro-electrodes, as illustratedin Figure 2. In order for corrosion to occur, the micro-cells must also be connected throughsome conducting path external to the metal. Usually the external connection is provided bywater or an aqueous solution and the cells produce a current, allowing the chemical reactionsresponsible for corrosion to proceed.
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