This study aims to modify the practice of using over-voltage concept of polarization process in cathodic protection to the potential of zero charges (Epzc) as a new technique of corrosion prevention. At Epzc, a metal surface is not in contact with an aqueous solution due to the absence of electrical charge and no electrostatic attraction. A chemical adsorption caused by oxidation reaction does not occur at Epzc· The removal of electrical charges at the electrode-electrolyte interface leads the desorption of ionic charges which causes the metal surface suffers no longer a corrosion reaction due to the absence of a charge transfers. The determination of Epzc is carried out by measuring the border line of adsorption and desorption of charged ions on the metal
surface by the intersected inducing polarization methods on the intermediate rod. The experimental Epzc value ( -703 m V vs SCE) is more negative than the corrosion potential (Ecorr = -701 mV vs SCE) shows the immersed metal in 3.5% NaCl solution have an excessive positive charge. Therefore, the negative charge is required to eliminate or neutralize the positive charges to bring the metal surface to Epzc· The charge removal is a discharging of double-layer process on the metal-solution interface. It is carried out by supplying electrons to the extent necessary just to eliminate the positive charges on the metal surface by using potentiostat. The discharging was perfmmed by means of voltage scan method around Epzc (Epzc scan) with an ideal magnitude at about 2 m V, which is slightly negative than corrosion potential (Ecorr) at the lowest rate (1.0 x 10-2 mV/ min). The plot of current density versus time takes about 100 hours to displays a capacitor discharging curve profile. The current requirement for corrosion protection at Epzc is not critical after a 100 hour period. The planned interval immersion tests on reactive Mg metals clearly prove that corrosion protection at Epzc is succeed and their corrosion protection efficiency is between 93-96% in 3.5 % NaCl solution.
