Figure 31 . Marine growth and corrosion products covering the surfaces of exposed 

 aluminum alloy (top) and steel (bottom) specimens on a plastic strip 

 (64 days). 



The effect on panels of exposure in the sea in various ways for 92 days 

 was similar to the effect of exposure for 64 days. However, the panels (other 

 than control panels) were covered with a larger and denser marine growth 

 (Figure 32). Two-inch-long hydroids, 1/2-inch-diameter barnacles, and numer- 

 ous 1/8-inch mussels were found on the panels. Microorganisms were again 

 isolated from inside cylinders containing control panels. During early parts of 

 the exposure period in the sea, dense growth of Ectocarpus (brown algae) was 

 noticed on the panels exposed for 64 and 92 days. The panels were free of 

 other marine growth. 



Seawater was found inside the nylon-screen-covered cylinders (both 

 the 64- and the 92-day) when placed on the deck of the pier; however, as 

 soon as the rubber stopper was removed, the seawater poured out through 

 the screen. The screen was covered with fine silt, debris and dense marine 

 growth. A layer of fine silt about 3/4-inch thick was found trapped at the 

 bottom section of the cylinders. The silt was probably washed through the 

 fine mesh screen openings during the early part of the exposure and was 



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