platinized metals. Graphite anodes are usually superior to high-silicon 

 cast iron for seawater installations whereas high-silicon cast iron 

 anodes are usually superior for fresh water installations (Husock, I962). 

 According to one report (Toncre and Rice, I966), high-silicon iron anodes 

 were selected over graphite anodes for brackish water installation after 

 running tests on the two types. Composition changes are continually 

 being made on basic anode materials to improve their performance. There- 

 fore, information on the relative merits of each type should be checked 

 just prior to selection. 



Cherry (1965) reports that graphite and silicon iron anodes suffer 

 breakage when subjected to heavy seas. If these anodes are placed on 

 the bottom, as is sometimes done to lessen their exposure to wave action, 

 their efficiency may be impaired due to increased anode to electrolyte 

 resistance caused by gas surrounding an anode which has been embedded 

 in mud. 



Platinized titanium anodes are apparently becoming popular in other 

 countries. Platinized titanium anodes have been tested (Toncre and Rice, 

 1966) and are expected to cut initial costs and operating costs of 

 cathodic protection systems. The long life of platinized titanium anodes 

 and the relative ease with which they can be installed are the factors 

 that are expected to reduce the costs of cathodic protection. Platinized 

 titaniiom anodes are generally used in the form of long thin rods . Copper 

 cores are used in platinized titanium anodes over 2 feet long to improve 

 their conductivity (Lowe, 1966). 



Toncre and Rice (1966) report that the copper cored platinized 

 titanium anodes presently in use by one company are 1/8 inch in diameter 

 and have platinum coatings 0.0001 to 0.0002 inch thick. The average 

 current density was reported to be of the order of 120 amperes per square 

 foot. These anodes, most of which were installed vertically, have been 

 in operation for up to 33 months with no apparent loss in their current 

 capacity. Laboratory tests were performed to discover why corrosion of 

 the titanium allowed two anodes to fall to the bottom. Observations 

 reported from these tests are that: 



1. If the copper core is exposed to the electrolyte, there 

 is no loss in anode efficiency when the copper core is 

 consumed if the anode has no mechanical load below the 

 exposed copper core. 



2. If under the same conditions, a mechanical load is placed 

 below the point of copper core exposure, the anode will 

 dissolve anodically near the break and quickly fail. 



Another report. Cherry (1965 ), states that after 5 years of service 

 there are indications that platinized titanium anodes should last in ex- 

 cess of 10 years. The most successful suspension system for these anodes 

 reportedly utilized steel pipe with an unplastisized polyvinyl chloride 



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