Although pure lead has been tested as an anode in seawater, it has not been successful because a PbCl2 film forms under the PbO2 oxide, separating and insulating the PbO2 from the lead substrate. It is essential to form and maintain the PbO2 layer on the surface of the anode, and therefore lead is alloyed with other metals such as silver, which make this layer more stable. This layer causes the current to spread and the lead acts only as a conductor and source of PbO2 formation.

Lead-silver anodes are designed for use in cathodic protection current injection systems and are made of high purity materials. They are suitable for use in marine industries due to their low corrosion rate and high flow rate. The weight of these anodes makes them easy to submerge in marine environments. PbO2 oxide is insoluble in sea water.

Lead-silver anodes are made in different shapes and according to their shape and weight, they are immersed (restrained by a rope) or installed by special holding devices near the structure under protection.

The chemical composition of lead-silver anodes according to MIL-A-23871A specification is as follows:
1) Pb-1Ag
Pb-1Ag alloy is suitable for use in seawater provided that the current density does not exceed 100-200 A/m2 and PbCl2 is formed at higher current densities. Lead consumption rate is about 0.1 kg/amp.year in sea water.

2) Pb-6Sb-1Ag
Pb-6Sb-1Ag alloy shows lower consumption rate and stronger PbO2 layer than Pb-1Ag alloy. The current density of these anodes is 160-220 A/m2 and their consumption rate is 0.09 kg/amp.year in sea water.