A cathodic protection system with external source has been installed to four open-type box-coolers in the Kawasaki Refinery of the Showa Petroleum Co.
Direct currents of 2.0-3.0 volts supplied from a selenium rectifier were applied to the surfaces of steel pipes and tanks through the steel anodes immersed vertically into the cooling sea water.
As the results of determining the potential differences between protected steel surfaces and adjacent water, it was confirmed that the potential distribution was fairly good, showing in every part far more negative potential than -0.77 volt referred to saturated calomel. These potentials moved considerably to the negative side with the lapse of time as a result of increasing cathodic polarization.
As a basic data for design, the adequate protecting current was estimated to be 0.1 ampere per sq. meter of protected surface.