COPPER ALLOYS 



The chemical compositions of the copper alloys are given in Table 

 4 and their corrosion rates in Table 5. The effects of depth, concen- 

 tration of oxygen in seawater and time on the corrosion rates are 

 shown graphically in Figures 10 through 12. 



Copper alloys corrode uniformly, hence corrosion rates calculated 

 from weight losses and reported as mils per year reflect the true con- 

 dition of the alloys. Therefore, corrosion rates for the copper alloys 

 can be used reliably for design purposes. However, this does not apply 

 to the copper base alloys which are susceptible to parting corrosion. 



The variation of the corrosion rates of copper and the copper 

 alloys with depth in the Pacific Ocean are shown in Figure 10. Since 

 the corrosion rates of all the copper alloys, except those attacked by 

 parting corrosion, were so comparable, the average values were plotted 

 in Figure 10. The corrosion of copper was insensitive to depth as well 

 as to the changes of concentration of oxygen in seawater at depth as 

 shown in Figure 10. The oxygen concentration curve was included in 

 Figure 10 to show its variation with depth and to show whether the cor- 

 rosion rate curves were of comparable shape. The average corrosion 

 rate curve for the copper alloys, although showing a slight decrease 

 with depth, did not decrease gradually; hence it is more oxygen than 

 depth dependent. The corrosion rates of only one alloy, Nickel-Silver 

 #752, increased gradually with increasing depth, Figure 10; hence its 

 corrosion is mostly depth dependent. 



The corrosion of copper was independent of the concentration of 

 oxygen in seawater as shown in Figure 11. However, the corrosion of 

 the copper alloys decreased slightly with decreasing concentration of 

 oxygen in seawater. 



The corrosion rates of copper and the copper alloys decreased with 

 increasing time of exposure in surface seawater as shown in Figure 12. 



The following alloys were attacked by parting corrosion in sea- 

 water: commercial bronze, red brass, Muntz metal, manganese bronze A 

 and nickel-manganese bronze, containing from 10 to 42 percent zinc, 

 were dezincified; aluminum bronzes containing 5, 7, 10, 11 and 13 per- 

 cent aluminum were dealuminified. 



NICKEL ALLOYS 



The chemical compositions of the nickel and nickel alloys are 



given in Table 6 and their corrosion rates and types of corrosion in 



Table 7. The effects of depth, concentration of oxygen in seawater 

 and time are shown graphically in Figures 13 to 19. 



In stagnant seawater and underneath fouling many of the nickel 



alloys are attacked by pitting and crevice corrosion in addition to 



general surface attack. Under the same conditions some of the more 



