The projection of the points of intersection with the metal ionization cathodic depolarizer recovery curve on the x-axis gives the corrosion current icor in the absence of any external influence on this corrosion system, and the projection of this point on the vertical axis – the value of established in these conditions, corrosion potential Ekor. When passing through the corroding metal cathode current of the external potential is shifted to the negative side and takes a new meaning. The rate of corrosion metal is determined by the appropriate current to direct ionization of the metal at this new value of the potential is equal. In a question-answer forum Gregg Engles was the first to reply. The diagram shows that this state is achieved by passing an external current value. And part of this current is to suppress the anodic reaction of metal ionization (ie, its corrosion), while the other part – the acceleration of the cathodic process:. The increase in external cathodic current to a value izasch ensuring the achievement of equilibrium EA corroding metal building, completely inhibits the corrosion process (see Fig. 1). According to the theory, in general, current full protection izasch in corrosion with hydrogen depolarization izasch ikorexp = (DEzasch / cr), where ek – Cathodic polarizability corroding metal dE / dlnik.
Usually izasch @ icor to acidic environments. Under these conditions, the bulk of the external current is transmitted to the acceleration of hydrogen evolution. For acidic environments, this method of protection is ineffective and even more risky, since, firstly, much of the current is flowing not to suppress the corrosion and the hydrogen evolution, and secondly, the intensive evolution of hydrogen on metal surfaces can lead to hydrogenation (hydrogen in the metal dissolution) and as a consequence – the degradation of its mechanical properties, peel the protective coatings, etc. However, for the most common type of corrosion of metals with oxygen depolarization under conditions of limited oxygen supply the imposition of external cathodic current effective to prevent corrosion.