Potential of Zero Charge (Epzc) is a characteristic value of the electrode potential for any metal at which a surface of the metal will not acquire an electrical charge when it comes into contact with an electrolyte. At the EPZC, there is no or very limited current flow. The adsorption of excessive positive and/ or negative charge to the metal surface that induced the corrosion reaction is suppressed. The surface tension is at a maximum, and the electrical capacitance at the boundary is at a minimum. A metal with excess positive charge on the surface can be made at zero charge when the positive charges on the surface are mutually neutralized by giving electrons to the metal. The charge neutralization process is done by applying an automatically controlled pulse and reverse pulse of capacitive current to fix the potential slightly below the corrosion potential, Ecorr. The pulse discharging can be carried out by using electronic equipment which is able to control and fixed the potential between the protected metal and a reference electrode to a constant value just slightly below Ecorr (at Epzc).
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