The current output of full-scale arrays of several anode sizes in use by the U. S. Navy for the cathodic protection of ship hulls were determined. Impressed-current anodes formed from sheet steel were substituted for conventional galvanic anodes to reduce the weight and number of arrays necessary to obtain the desired information. Five anode sizes were investigated. A 1500-foot steel sea wall located in water with a resistivity of 34 to 38 ohm-cm acted as an unpolarizable cathode. The output currents were determined for driving potentials of 0.1, 0.2, 0.5, 0.7, and 1.0 between the cathode and the anode arrays; hence the data can be used to estimate for any galvanic material both the initial current output of an anode array, and the continuing current output against a cathode polarized to a known potential.
The anodes in all arrays investigated suffered mutual interference as indicated by decreased current outputs from individual anodes as the number of anodes in the array increased. It was found that the addition of anodes is more efficient than a moderate separation of anodes in increasing the total current output.
An empirical equation was derived from the data of the continuous linear arrays which relates the current output to total anode area and driving potential. It may be used to estimate the current output of arrays for which more specific data have not been obtained, but these estimations should be confirmed by experimentation wherever possible. 5.2.2
