Pure Pb has been tried as an anode in seawater but fails to passivate, since PbCl₂ film forms beneath PbO₂ layer and insulates the PbO₂ from Pb substrate. Formation and maintenance of PbO₂ on anode surface is essential and therefore alloys Pb with other metals such as Ag that make this layer more stable. This layer releases current and leads to Pb only as a conductor and source of PbO₂.

Pb-Ag anodes are designed for use in impressed current cathodic protection systems and are made of high-purity materials. They are suitable because of the low corrosion rate and high flow rates for use in marine industries. The weight of these anodes makes them immersed in marine environments. PbO₂ in seawater is insoluble.

Pb-Ag anodes are made in different shapes and are fitted under the protection according to the shape and weight of the anodes in the form of immersion (harnessed by a rope) or by special preservative devices adjacent to the structure.

The chemical composition of Pb-Ag anodes in accordance with MIL-A-23871A is as follows:

1) Pb-1Ag

Pb-1Ag alloy is suitable for use in seawater providing that the current density did not exceed 100-200 A/m² and at high current densities PbCl₂ formed. The consumption rate is about 0.1 kg/amp.year in seawater.

2) Pb-6Sb-1Ag

Pb-6Sb-1Ag alloy gave a lower consumption rate and exhibited a harder PbO₂ layer than Pb-1Ag alloy. The current density of these anodes is 160-220 A/m² and the consumption rate is 0.09 kg/amp.year in seawater.