The Effect of Nitrite to Anode Reaction Property in Chloride-Induced Macro-Cell Corrosion

This research recorded the polarization process of chloride-induced macro-cell corrosion, and polarization ratios and slopes are utilized to reveal the macro-cell inhibiting mechanism by nitrite. The results indicate that the corrosion is mainly controlled by anode and the influence of cathode is tiny in the typical macro-cell corrosion of large cathode and small anode. With the increasing of nitrite concentration in anode, the macro-cell corrosion will be more controlled by anode and the macro-cell current density will be decreased to a lower level. Moreover, the existence of nitrite in anode under the circumstance of chloride-induced macro-cell corrosion can dramatically escalate the anode polarization slope which is the key determinant of the macro-cell corrosion current density decreasing. Additionally, with the increasing of nitrite concentration, the decreasing of macro-cell potential difference will not be appeared in the initial inhibiting period but can be appeared in later inhibiting period. Compared with decreasing of macro-dell potential difference, increasing of anode polarization slope is the main reason to decrease macro-cell corrosion current density.