depth) was of the same aggressiveness as the higher oxygen environ- 

 ment (6,000 foot depth). 



There was neither pitting nor crevice corrosion of this alloy 

 at a depth of 5,600 feet in the Atlantic Ocean. In fact, there 

 was no visible corrosion after 1050 days of exposure, Figure 5. 

 This excellent resistance to corrosion at a depth of 5,600 feet in 

 the Atlantic Ocean indicates that the environment at this location 

 is different from the environment at a depth of 5,500 feet in the 

 Pacific Ocean, The oxygen concentration in the Atlantic has been 

 reported as 5.7 milliliters per liter (at least as high as at the 

 surface) and no fouling organisms were reported, but, in addition 

 the current must have been high enough to prevent stagnation: all 

 three conditions are usually necessary to prevent pitting. 



There was a similar variability in corrosion rates of the 

 nickel-copper 400 alloy partially embedded in the bottom sediments 

 which is also attributed to the crevice and pitting types of corro- 

 sion. At the 5,500 foot depths the depths of the pits and the 

 severity of the crevice corrosion increased with increasing duration 

 of exposure. 



When nickel-copper 400 alloy was welded with filler metal 60 

 by the inert gas welding process the weld bead both in the sea water 

 and in the bottom sediment after 402 days of exposure at a depth 

 of 2,370 feet was selectively attacked as shown in Figure 7. When 

 welded with electrodes 130 and 180 by the metal-arc welding process 

 the weld beads were not selectively corroded, the corrosion was 

 uniform and no more severe than that on the unwelded sheet. 



Nickel-copper alloy 400 was not susceptible to stress corrosion 

 cracking when exposed at stresses equivalent to 50 and 75 percent of 

 its yield strength for 402 days at a depth of 2,370 feet. 



The mechanical properties of the unwelded nickel-copper 400 

 alloy were not impaired by exposure at nominal depths of 2,500 and 

 6,000 feet for periods of time of 402 and 1064 days, respectively 

 except after 751 days at 5,500 feet. Table 7. The 22 percent de- 

 crease in the elongation after 751 days of exposure at a depth of 

 5,500 feet was due to the deep pits. 



The percent elongation of the welded specimens decreased with 

 attendant increases in the yield strengths as shown in Table 7, 

 This is not considered significant except for the specimen in the 

 sea water welded with filler metal 60 which broke in a weld defect. 



Nickel-copper alloys 402, 406, and K-500 behaved much the 

 same as the 400 alloy in that their corrosion rates vacillated 

 between less than 0.1 and 1.5 MPY due to the severity of crevice and 



