Presented in this report are the results of a long-term marine exposure 

 study which was conducted to determine the effects of marine fouling on the 

 corrosion rate of 1010 carbon steel and 7178-T6 aluminum alloy. The test 

 panels were exposed at the surface of the sea and also on the seafloor in 6,000 

 feet of water. To compare the corrosion rates between fouling-free panels and 

 heavily fouled panels, the fouling-free or control panels were placed inside a 

 specially designed initially sterile cylindrical test chamber sealed with 

 0.45-micron porosity membrane filters. For maximum fouling effects, the 

 unprotected or exposed panels were secured to plastic strips and exposed 

 to the seawater environment. Other test panels were exposed at the surface 

 of the sea by placing them inside plastic cylinders with ends covered with a 

 fine mesh plastic screen and also inside cylinders with ends left uncovered. 

 The latter two tests were conducted primarily to determine the effects of 

 tidal currents on corrosion and to compare the corrosion rates with exposed 

 panels. The latter panels would all be subjected to attachment by various 

 marine fouling organisms and to the effects of other marine environmental 

 factors. 



Seawater samples were collected from inside recovered test chambers 

 sealed with membrane filters and analyzed for dissolved oxygen concentration, 

 pH, salinity and water temperature. Seawater samples from 10 feet below the 

 surface of the sea (at high tide) and also from 6,000 feet below the surface of 

 the sea were collected and similarly analyzed. Bacteriological analyses were 

 also conducted on these seawater samples. The information about the sea- 

 water environment in which the test panels were exposed is essential in 

 evaluating corrosion of metals and metal alloys. 



For exposure of test specimens on the seafloor in 6,000 feet of water, 

 the specimens were placed on a Submersible Test Unit (STU) and it was 

 emplaced on the deep-ocean floor in the Pacific Ocean for a period of 189 

 days (6.3 months). 



MATERIALS AND EXPERIMENTAL METHODS 



Preparation of Test Specimens 



The test specimens used in this study were made of 1010 carbon steel 

 and 7178-T6 aluminum alloy and measured 1/8 X 1 x 3 inches. Some6-inch- 

 long specimens were also used. A 1/4-inch-diameter hole was drilled at each 

 end of the panels for assembly purposes. The test panels were treated as 

 follows before exposure in the sea; 



