To extend the cathodically protected area with impressed current, strip-type anode and the coating around the anode has been examined through mathematical calculation and a simulation tank experiment. The following main trends have been observed.
1) A method for calculating the potential distribution is presented and the formula obtained has been shown reasonable by the experiment.
2) Steel surface coated with an insulation coating around the anode gives the equivalent effect as an enlarged anode having the same area.
3) As for a coating material around the anode, neoprene rubber lining of 1mm thickness can be adopted.

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Injection of electrolytically produced chlorine into sea water is one of the effective means to prevent heat-exchangers and pipelines from fouling with marine organisms.
This paper relates mainly to the chlorine evolution efficiency on a Pb-2.07% Ag anode in the electrolysis of the artificial sea water.
The chlorine evolution efficiency from the artificial sea water is 55-75per cent at current densities of 10-200mA/cm². The potential of the Pb-Ag anode increases considerably near a current density of 200mA/cm² to result in reduction of corrosion resistivity of the anode.
The corrosion resistivity of the anode practically disappears in the two-fold diluted sea water with reduced chlorine evolution efficiency. When degree of dilution reaches to 10, the anode simply dissolves without forming lead peroxide layer on the surface.
It is concluded that chloride ions are oxidized on the surface of lead peroxide, because the evolution of chlorine gas and stabilization of the anode potential are observed only after the formation of lead peroxide. The lead peroxide layer on the anode is found to be stabilized by the presence of sulfate ions in the electrolyte.
An example is given on the anti-fouling system by electrolytic chlorination using Pb-Ag anode.

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