In the design of cathodic protection systems for water tanks, using an external source of direct current, it is necessary to select a metal from which the permanent anodes are to be fabricated. With the large number of metals and alloys now commercially available, the engineer has a wide selection and it is advisable that he have available data pertaining to the destruction rate of these metals at the approximate conditions of operation. According to Faraday's law, during electrolysis, a metal is destroyed in proportion to its equivalent weight, and the product of the time current flow. This relationship is true if the metal is pure, being electrolized in a solution of its ions, and polarization and other effects eliminated. In water tank cathodic protection systems, these conditions are never present. This paper presents corrosion data on a number of commercial metals and alloys used as permanent anodes. Investigations were made in water of pH 6.3 and 8.6; the latter having a higher alkaline earth content. The data are presented in both table and graphic form. Corrosion rate data are presented in pounds per unit current density per year. The current density range for each metal studied was from 1/4 to 4 amps, per sq. ft.

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Copyright 1950 by the National Association of Corrosion Engineers.
1950
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