tension is relieved in an infinitely small current and new portions of the metal pass into solution; otherwise the action is arrested by the non-conducting quality of the thin film of hydrogen.

The presence of minute particles of suitable impurities in or on the iron, whose solution tension differs from the iron, or the presence of acids in the water, facilitates the discharge of the electric tension, and hence, the continuous removal of particles of iron. On the other hand, the presence of alkalies, and a few other substances that decrease hydrogen ion concentration, will diminish or even stop iron solution and rusting altogether.

This, in brief, is the substance of the electrolytic theory of rusting, the more complete explanation of which would involve the  details  and  language of the ionic theory