Action in a concentration cell is described briefly and shown in an accompanying diagram. A case involving attack on lead cable sheath by differential aeration cell action is described. The center portion of the cable was not attacked because it was pressed tightly against the inner surface of the tile duct. During the time the cable was in this position, water of varying amounts formed a meniscus extending from the sheath surface to the tile and reaching all the way around the dry area. Immediately outside of the area pressed against the tile, the lead had been removed by anodic action.
A case involving galvanic corrosion of a lead telephone cable sheath is discussed. It was found that the moisture seal over the lead and steel had been destroyed, exposing the metal coverings to attack by electrolytes of the soil. The effect of pH on polarity of lead and iron in a common electrolyte is shown in a diagram.
