pitting corrosiono After 1096 days of exposure at the surface in 

 the Atlantic Ocean, Harbor Island, North Carolina, the corrosion 

 rate of nickel-copper alloy K-500 was 0.8 MPY which compares 

 favorably with its behavior at depth in the Pacific Ocean, Most 

 of the corrosion at the surface was also due to localized corrosion. 



Cast nickel-copper alloys 410 and K-505 corroded uniformly as 

 shown in Table 6. The corrosion rates of the cast-410, in general, 

 decreased with an increase in the time of exposure at both depths, 

 2,350 and 5,500 feet as shown in Figure 8, and in both cases the 

 corrosion rates in the bottom sediments were less than those in the 

 sea water at the same depth. After 1064 days of exposure at a 

 depth of 5,300 feet the corrosion rates in the sea water and in the 

 bottom sediment were about the same. The corrosion rates at a 

 depth of 2,350 feet were less than those at a depth of 5,500 feet. 

 Initially the cast nickel-copper K-505 alloy corroded at a greater 

 rate in the bottom sediment than in the sea water but after 1064 

 days of exposure at a depth of 5,500 feet, it was lower than in 

 sea water as shown in Figure 9. The general trend was for the 

 corrosion rates to decrease as the duration of exposure increased. 

 The corrosion rates at 2,350 feet were lower than those at 5,500 

 feet. 



Nickel-copper 60 alloy was attacked by the crevice type of 

 corrosion at both depths, Table 6. In most cases the crevice corro- 

 sion was greater on the specimens exposed in the sea water than on 

 those partially embedded in the bottom sediments. 



X-ray diffraction, spectrochemical and chemical analyses of 

 corrosion products removed from nickel-copper alloys 400 and K-500 

 showed that they were composed of cupric oxide (CuO) , nickel oxide 

 (NiO) , nickel hydroxide (Ni(0H)2), cupric chloride (CUCI2) , copper- 

 oxy-chloride (CuCl2.3CuO.4H2O), a trace of nickel sulfide (NiS) and 

 phosphate, chloride and sulfate ions. 



NICKEL ALLOYS 



The chemical compositions of the nickel alloys are given in 

 Table 8, their corrosion rates and types of corrosion in Table 9, 

 their stress corrosion resistance in Table 10 and changes in 

 mechanical properties in Table 11. 



There were no significant weight losses or any visible corro- 

 sion on any of the following alloys: 



a. Ni-Cr-Fe 718, unwelded and welded 



