RESISTANCE OF MATERIALS TO MARINE BIOLOGICAL ATTACK 1111 



terials as a carbon source in sea water. There is little or no opportunity 

 for ecological factors to come into play, however, particularly with re- 

 gard to marine sediment. In the conductor test, sea water and marine 

 sediment form a part of the test environment, and the test is run over 

 a much longer period of time, thus encouraging more natural and dy- 

 namic organism associations. Likewise, the natural relationship between 

 material and environment is simulated more closely than it is in the more 

 accelerated test. In these respects, the conductor test is intermediate to 

 the BOD-type test and natural marine exposure. 



The material to be tested is coated on a conductor to provide about 

 10 mils of insulation. A standard coil of this insulated conductor is then 

 exposed in a 16-ounce bottle so that half of the coil is in marine sediment, 

 and half is in sea water. The ends of the coil are brought through holes 

 in the bottle cap and attached to terminals in the cap. The general 

 features of the test setup are shown in Fig. 5. The bottle is incubated at 

 20°C. Capacitance and conductance measurements, taken monthly, in- 

 dicate any change in the insulation. Some conductors are placed in 

 sterile sea water and sediment to serve as controls. This type of test can 

 be continued for months or years if necessary. 



Most of the conductor tests are now being initiated. Two materials, 

 however, GR-S and a rigid polyvinyl chloride, have been under study 



Table XIII — Summary of Materials Utilized as Source of 



Carbon by Aerobic or Anaerobic Marine Bacteria 



IN BOD-Type Test 



Utilized as Source of Carbon by 



