linearly with increasing duration of exposure, while 

 corrosion attack was constant in seawater and in the 

 bottom sediments with increasing duration of expo- 

 sure at the 2,500-foot depth. Corrosion at the 

 2,500-foot depth was slighdy less rapid than at the 

 surface or the 6,000-foot depth. Corrosion in surface 

 seawater decreased at a more rapid rate than at depth. 

 The differences in the corrosion rates of the copper- 

 nickel alloys in the different environments were so 

 small that, for practical purposes, they can be con- 

 sidered to be the same. 



3.4.2. Effect of Depth 



The effect of depth on the corrosion of the 

 copper-nickel alloys after 1 year of exposure in sea- 

 water is shown in Figure 9. Depth exerted no influ- 

 ence on the corrosion of the copper-nickel alloys 

 during 1 year of exposure, at least to a depth of 

 6,000 feet. 



3.4.3. Effect of Concentration of Oxygen 



The effect of the concentration of oxygen in sea- 

 water on the corrosion of the copper-nickel alloys 

 after 1 year of exposure is shown in Figure 10. The 

 corrosion increased slightly with increasing oxygen 

 concentration during 1 year of exposure. 



3.4.4. Effect of Iron 



Copper-nickel alloys with iron contents varying 

 between 0.03 and 5% were among the alloys in this 

 program. The effects of iron on the corrosion of these 

 alloys after 400 days and 1,064 days of exposure at 

 the 6,000-foot depth are shown in Figure 14. 

 Generally, the rates of corrosion decreased with 

 increasing iron content. 



3.4.5. Stress Corrosion 



Four copper-nickel alloys were exposed in sea- 

 water to determine their susceptibility to stress 

 corrosion under the conditions given in Table 24. 

 They were not susceptible to stress corrosion. 



3.4.6. Mechanical Properties 



The effects of corrosion on the mechanical pro- 

 perties of five copper-nickel alloys are given in Table 



25. The mechanical properties were not adversely 

 affected during exposure at the depths and during the 

 rimes of exposure given in Table 25. 



3.4.7. Corrosion Products 



Chemical analyses of the corrosion products 

 removed from 70% copper-30% nickel-5% iron 

 exposed for 751 days at a depth of 6,000 feet showed 

 that they were composed of nickel hydroxide 

 (Ni(OH) 2 ); cupric chloride (CuCl 2 ); major elements, 

 copper and nickel; minor elements, iron, magnesiun, 

 sodium, and traces of silicon, and manganese; 

 chloride ion' as CI, 4.77%; sulfate ions as S0 4 , 0.80%; 

 copper as metal, 43.63%. 



3.5. ALL COPPER ALLOYS 



The effects of the duration of exposure on the 

 corrosion of all the copper alloys in seawater at the 

 surface and at the 6,000-foot depth are summarized 

 in Figure 15. Their rates of corrosion decreased 

 essentially linearly with increasing duration of 

 exposure. Their rates were also comparable and were 

 essentially the same after 1,064 days of exposure. 



The corrosion of all the copper alloys was not 

 affected by depth as shown in Figure 9. 



The corrosion of copper and the silicon bronzes 

 was not influenced by changes in the concentration 

 of oxygen in seawater during 1 year of exposure, 

 while that of the other alloys increased with 

 increasing oxygen concentration, as shown in Figure 

 10. 



None of the copper alloys were susceptible to 

 stress corrosion. 



The mechanical properties of copper, the 

 beryllium-copper alloys, copper-nickel alloys, 

 phosphor bronzes A and D, and Arsenical Admiralty 

 brass were not adversely affected by exposure in sea- 

 water either at the surface or at depth. Those of 5% 

 aluminum bronze, silicon bronze A, Muntz Metal, and 

 nickel-manganese bronze were adversely affected. 



Aluminum alloy 7075-T6 was galvanically cor- 

 roded when in contact with beryllium-copper. 



All the brasses containing from 10 to 42% zinc, 

 except Arsenical Admiralty, aluminum brass, nickel 

 brass, all the aluminum bronzes, and the silicon 

 bronzes, were attacked by parting corrosion. 



47 



