Critical anode current

Spontaneous Passivation The anodic nose of the first curve describes the primary passive potential Epp and critical anodic current density (the transition from active to passive corrosion), if the initial active/passive transition is 10 lA/cm or less, the alloy will spontaneously passivate in the presence of oxygen or any strong oxidizing agent. 

Critical Anode Current Density anodic current density that must be exceeded in order to produce an active to passive transition (for a given metal it varies with the nature of the solution, temperature, velocity, etc.). 

Figure 2 Typical anodic dissolution behavior of an active-passive metal. ZJpp = primary passivation potential, iait = critical anodic current density, and ipass = passive current density. (After Ref. 71.)...

The effect of acid concentration on polarization of active-passive metals is shown in Fig. 4.8. Higher hydrogen ion concentration increases the critical anodic current density and decreases the passive potential range. Severe corrosion conditions present at higher acidity also increase current densities and corrosion rates at all potentials. Figure 4.9 presents the data for iron passivation in phosphoric acid/phosphate buffer solutions of... 

FIGURE 15.3 Schematic Evans diagram for the behavior of an active-passive metal. (m/m )> reversible potential of the couple o(m/m+)> exchange current density Epp, passivation potential trio critical anodic current density ip, passive current density Ef, transpassive potential. 

The potential corresponding to the maximum active current density (critical anodic current density) of an electrode that exhibits active-passive corrosion behavior. 

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