rates were the same in the sea water and in the bottom sediments, and 

 decreased asymptotically with increasing time of exposure at the 6,000 

 foot depth as shown in Figure 39. At the 2,500 foot depth, the cor- 

 rosion rate in sea water was uniform with increasing time of exposure 

 and was the same as at the 6,000 foot depth after 400 days of exposure. 

 In the bottom sediments at the 2,500 foot depth, the corrosion rate in- 

 creased slightly with time of exposure and after 400 days was the same 

 as at the 6,000 foot depth. 



The corrosion rates of 80 copper-20 nickel alloys are shown in 

 Figure 40. The alloys differed in chemical composition with regard to 

 their iron contents; the one exposed by NCEL contained 0.62 percent 

 iron while the one exposed for the International Nickel Company, Inc. 

 contained 0.03 percent iron. The differences in their corrosion rates 

 are attributed to the difference in their iron contents. This is 

 clearly shown in Figure 40 where, in sea water at both depths, the 

 corrosion rates of the alloy with 0.03 percent iron were higher than 

 those of the alloy which contained 0.62 percent iron. The reverse was 

 found in the specimens exposed in the bottom sediments. The corrosion 

 rate of the alloy with 0.03 percent iron after 181 days of exposure at 

 the surface in the Pacific Ocean was higher than those for the same 

 alloy at both depths. The corrosion was, in general, uniform. 



The corrosion rates of 55 copper-45 nickel alloy (a thermocouple 

 alloy) are shown in Figure 41. The alloy corroded uniformly except for 

 crevice corrosion to perforation after 1064 days of exposure in the 

 bottom sediment at the 6,000 foot depth. The corrosion rates initially 

 increased with time, then became constant at about 1.0 MPY at the 

 6,000 foot depth in sea water while in the bottom sediments, they 

 initially decreased with increasing time of exposure, then became con- 

 stant at about 0.5 MPY. At the 2,500 foot depth the corrosion rates 

 both in sea water and in the bottom sediments decreased with increase 

 in duration of exposure. At both depths the corrosion rates in the 

 bottom sediments were lower than those in the sea water. After 181 days 

 of exposure at the surface in the Pacific Ocean, the corrosion rate of 

 the alloy was much higher than at either depth. 



The corrosion rates of a nickel-silver (65 Cu - 18 Ni - 17 Zn) are 

 shown in Figure 42. At the 6,000 foot depth, the corrosion rates both 

 in sea water and in the bottom sediments decreased rapidly with in- 

 creasing time of exposure. The corrosion rates at the 2,500 foot depth 

 were essentially constant with time and those in the bottom sediments 

 were very low and much lower than those in the sea water. After 181 

 days of exposure at the surface and 197 days of exposure in the sea 

 water at a depth of 2,500 feet in the Pacific Ocean, the corrosion rates 

 were practically the same. The corrosion rate of this alloy at the sur- 

 face in the Pacific Ocean at the Panama Canal Zone was very low (0.03 

 MPY) and constant with time of exposure. The type of corrosion was 

 uniform. 



The corrosion rates of a copper-nickel-zinc-lead alloy are shown 



16 



