of the corrosion rates of the steels exposed at a depth of 5,500 

 feet in the Pacific Ocean indicates that the environment in the 

 Atlantic Ocean is somewhat different from the environment in the 

 Pacific Ocean. The median curve of corrosion rates for the 2,350 

 foot depth is below that for the 5,500 foot depth indicating a dif- 

 ference in environments even though the confidence limits overlap. 

 In the case of the median corrosion rates curves for the specimens 

 in the bottom sediments (Figure 8), the median values are the same 

 after 400 days of exposure indicating that the environments are 

 nearly identical. The median corrosion rate curves for the 2,350 

 foot and 5,500 foot depths are shown in. Figure 9. Between 200 and 

 400 days of exposure the corrosiveness of the bottom sediment at 

 5,500 feet was the same as the sea water at the 2,350 foot depth. 

 After 400 days of exposure the bottom sediments at the 5,500 foot and 

 2,350 foot depths and the sea water at the 2,350 foot depth were of 

 equal aggressiveness. After 751 days of exposure at the 5,500 foot 

 depth, the sea water and bottom sediment environments were similar 

 with regard to their effect on the corrosion of steels. Since no 

 data are available for the 2,350 foot depth for periods of exposure 

 beyond 400 days it is not possible to correlate the corrosion of 

 steels at the two depths beyond this duration of exposure. 



Variations of from 1,5 to 9 percent in the nickel content of 

 steel were ineffectual with respect to the corrosion rates as shown 

 in Figure 10, 



The corrosion rates of AISI Type 502 steel (5% Cr-0.5% Mo) were 

 erratic and higher than for the other steels. This behavior is attri- 

 buted to the broad shallow pitting and severe crevice corrosion at 

 insulators and fasteners. 



The corrosion rate for a nickel-cobalt high strength (190 KSI) 

 alloy steel was within the limits shown for other alloy steels in 

 Figure 5 for 402 days of exposure at a depth of 2,370 feet. 



Specimens of two heats cf 18% Ni maraging steels from NCEL and 

 one heat from INCO were exposed for 402 days at a depth of 2,370 

 feet. The 0.08 inch thick material from one NCEL heat was aged at 

 900''F for three hours and air cooled, then a portion was welded. 

 This material, both unwelded and welded corroded at twice the rate 

 of the material from the other heats, 3.2 MPY vs 1„4 MPY. The 

 material aged by NCEL had a yield strength of 315 KSI while the yield 

 strengths of t?ie heats aged by the producer were in the range of 235 

 to 265 KSI. The corrosion was uniform with tightly adhering films of 

 black corrosion products. 



