1. The carbon steel panels were cleaned in an ultrasonically vibrated tank 

 containing 10%, by weight, ammonium citrate solution heated to 150°F. 

 The panels were then washed in hot running water, scrubbed with a fiber 

 bristle brush, washed in hot running water, dipped into distilled water, 

 rinsed in absolute ethyl alcohol, and then dried in a current of warm air. 



2. The aluminum alloy panels were cleaned in an ultrasonically vibrated tank 

 containing concentrated nitric acid at room temperature, and then washed, 

 scrubbed, rinsed, and dried similarly to carbon steels. 



3. The cleaned panels were weighed, measured, and stored in a room in which 

 the relative humidity was maintained at 20%. 



4. Prior to assembly and placement inside test chambers, the test panels were 

 sterilized by dipping in ethyl alcohol. These were assembled together (2 to 



4 panels) by inserting nylon rods through the holes located at both ends of the 

 test panels. The metal panels were kept apart with short pieces of vinyl tubing 

 placed between the test panels over the nylon rod to prevent galvanic corrosion. 



Design of Plastic Test Chambers 



As shown in Figure 1, the test chambers were made from a 1/4-inch- 

 thick, 4-inch diameter, clear, transparent acrylic plastic tubing cut into 2-inch 

 lengths. A 1-inch diameter hole was drilled through the cylinder wall and it 

 was plugged with a rubber stopper (water samples were obtained through this 

 hole). The open ends of the cylinders were treated in different ways as follows: 



1. Covered with 0.43 -micron porosity membrane filters. The thin 

 filters were sandwiched in between two 210-mesh (0.0083-inch) nylon screen 

 cloths to prevent rupture. These were in turn placed between two plastic end 

 plates (Figure 1 ) and cemented together around the edges with a silicone adhe- 

 sive. The test panels were then secured inside the cylinder with these end plates 

 using machine screws. A silicone adhesive was used around the edges to serve 

 as a sealant and gasket to prevent leaks. The test chamber was specially designed 

 to facilitate continuous free exchange of seawater only through the membrane 

 filter. After the sterilized test panels were aseptically placed inside the test 

 chamber and both ends sealed with membrane filters, the chamber was filled 

 with seawater by either submerging it in the sea or by placing the test chamber 

 in a plastic container filled with filtered seawater. From laboratory tests, it was 

 found that it takes about 30 minutes to fill a 350-ml volume test chamber 

 (without a rubber stopper) with seawater flowing through the membrane filter; 

 also from laboratory tests, the dissolved oxygen concentration, salinity, and 



