while there were no significant effects at depth for comparable periods 

 of exposure. 



NICKEL ALLOYS 



The chemical compositions of the nickel alloys are given in 

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

 the effect of exposure on their mechanical properties in Table 10. 



Corrosion 



The corrosion rates, maximum and average pit depths, depth of cre- 

 vice corrosion and types of corrosion are given in Table 9. 



There was no visible corrosion on 14 of the alloys and their 

 corrosion rates were less than 0.1 MPY (mils penetration per year). 

 These alloys were: nickel-chromium-molybdenum alloys No. 3 and 625; 

 nickel-cobalt-chromium alloy 700; nickel- chromium- iron alloy No. 718; 

 nickel- iron-chromium alloys No. 800, 804, 825, 825 sensitized (heated 

 1 hour at 1200°F) , 825 Cb and 901; nickel-chromium-iron-molybdenum 

 alloys No. F, G and X; and nickel-molybdenum-chromium alloy No. C. 



The corrosion rates of 23 of the other 24 alloys were higher at 

 the surface than at both depths, 2,500 and 6,000 feet. The corrosion 

 rate of the other alloy, cast nickel-copper 505, was higher at the 

 surface than at the 2,500 foot depth but lower than at the 6,000 foot 

 depth. The corrosion rates of 14 of the alloys decreased as the depth 

 increased as shown in Figure 5. The averages of the corrosion rates of 

 the 14 alloys at the three depths along with the maximum and minimum 

 corrosion rates at each depth are plotted in Figure 5. However, for 10 

 of the alloys the corrosion rates were lower at the 2,500 foot depth 

 than at the 6,000 foot depth and the latter were lower than the corrosion 

 rates at the surface. The curves of the averages of the corrosion rates 

 of the 10 alloys at each depth in addition to the curves of the maximum 

 and minimum values are shown in Figure 6. 



Five of the alloys which were corroded during the surface exposure 

 were not attacked by crevice corrosion: nickel alloy 301; cast nickel- 

 copper alloy 505; nickel-copper alloy 55-45; nickel-molybdenum- iron 

 alloy B; and nickel-molybdenum alloy 2. There was crevice corrosion on 

 21 alloys which varied in intensity from a depth of 12 mils to perfor- 

 ation of 50 mil thick specimens. There was crevice corrosion on nickel- 

 iron-chromium alloy 825, whose corrosion rate was less than 0.1 MPY to 

 a depth of 33 mils at an intentional crevice and to a depth of 44 mils 

 underneath barnacles. 



The effect of the concentration of oxygen in sea water on the 

 corrosion of nickel alloys is shown in Figures 7 and 8. The corrosion 

 rates of 12 nickel alloys decreased as the concentration of oxygen in 

 the sea water decreased. The averages, and maximum and minimum cor- 

 rosion rates of these 12 alloys are shewn in Figure 7. The decrease in 



