The corrosion rates of test panels exposed for 70 days in the sea 

 are presented in Table 2. The corrosion rates of steel control panels were 

 1.12 mpy as compared to 1 3.80 mpy for exposed panels. The corrosion rates 

 of aluminum alloy control panels were 0.42 mpy as compared to 8.19 mpy for 

 exposed panels (Table 2). 



When bacteriological tests were conducted on seawater samples 

 collected from inside the initially sterile cylindrical test chambers, approxi- 

 mately 1 ,000 bacteria (single species) per ml of seawater were isolated. It 

 is not known what effect these bacteria had on the corrosion rates of control 

 test panels, nor is it known how or when the seawater became contaminated 

 with these microorganisms. 



Further bacteriological tests conducted on the bacteria collected from 

 the water samples showed that these were small gram-negative, spore-forming, 

 rod-shaped bacteria. These bacteria grew exceptionally well and rapidly in a 

 test tube containing nutrient broth made with seawater, but grew very slowly 

 and very poorly in a nutrient broth made with distilled water. Identical 

 bacteria were isolated from inside sterile test chambers used in Exposure 

 Tests nos. 2 and 3. 



Dissolved oxygen concentration was not determined from these water 

 samples because large amounts of air were introduced into the samples during 

 collecting operation. The automatic pipetting device was not available for use 

 at this time. 



The exposed steel and aluminum alloy specimens submerged in the 

 sea for 1 12 days were covered with a denser marine growth than the 70-day 

 panels. Fouling on the panels included barnacles, calcareous tubeworms, 

 branching and encrusting bryozoans, some algae, kelp, and corrosion products 

 (Figure 14). After the corrosion products and marine growth were removed 

 from these panels by washing, scrubbing, and cleaning in a chemical solution, 

 the steel showed some corrosion on the surface (irregular surface) as shown 

 in Figure 15. The aluminum alloy showed pitting on the surface (Figure 16) 

 and also severe corrosion along the edges of the panels (Figure 17). The steel 

 and aluminum alloy control panels were relatively free of corrosion and pitting 

 (Figure 18), but there was some corrosion along the edges of aluminum alloy 

 panels (Figure 19). The average corrosion rates for the 1 12 days of exposure 

 are presented in Table 2. Bacteria were again found in seawater samples in 

 which control panels were exposed. 



After 268 days in the sea, the exposed steel and aluminum alloy 

 panels were completely covered with a very dense growth of branching bryo- 

 zoans (Figure 20). Underneath this growth, other sessile organisms such as 

 tubeworms, barnacles, and encrusting bryozoans were found attached to the 

 surfaces of the test panels (Figures 21 and 22). The surfaces of the carbon 



17 



