corrosion rate is almost linear with the decrease in the concentration 

 of oxygen. The decrease of the average corrosion rates, and the maxi- 

 mum and minimum rates of 10 other alloys with decreasing concentration 

 of oxygen in the sea water are shown in Figure 8. In the case of these 

 10 alloys, the average corrosion rate at 1.3 ml/1 of oxygen was slightly 

 lower than at 0.4 ml/1 oxygen but there was an overall decrease in cor- 

 rosion rates as the concentration of oxygen decreased from 5.25 to 0.4 

 ml/1. 



The effect of exposure on the mechanical properties of the nickel 

 alloys is given in Table 10. The mechanical properties of four of the 

 alloys were not affected by exposure at the surface for 181 days, at a 

 depth of 2,500 feet for 197 days, and at a depth of 6,000 feet for 123 

 days. The elongation of nickel- iron- chromium alloy 902 was adversely 

 affected during 181 days of exposure in surface water immersion. 



STEELS 



The chemical compositions of the steels are given in Table 11, 

 their corrosion rates in Table 12, and changes in mechanical properties 

 due to exposure in the ocean in Table 13. 



The corrosion rates of all the steels were higher in surface waters 

 than at both depths of 2,500 feet and 6,000 feet, Table 12. The cor- 

 rosion rates at the 6,000 foot depth were greater than at the 2,500 

 foot depth. The effect of depth on the corrosion rates of the steels 

 is shown in Figure 9. The corrosion rates of the steels at each depth 

 were averaged to obtain an average corrosion rate for any one depth. It 

 is these average values which are plotted in Figure 9. Also shown in 

 Figure 9 are the maximum and minimum corrosion rates for each depth to 

 indicate the spread in the values. 



The average corrosion rates and, the maximum and minimum corrosion 

 rates were also plotted against the concentration of oxygen in sea 

 water from Table 1 to show the effect of oxygen on the corrosion rates 

 of steels. This is shown in Figure 10 where it is clearly evident that 

 the corrosion rates of the steels decrease with decreasing concentration 

 of oxygen in sea water. The average corrosion rate at the surface is 

 5 times greater than at a depth of 2,500 feet and 2.7 times greater than 

 at a depth of 6,000 feet. 



The effect of exposure at the surface and at depths of 2,500 and 

 6,000 feet on the mechanical properties of some of the steels are 

 given in Table 13. The mechanical properties were not affected. 



CAST IRONS 



The chemical compositions of the cast irons are given in Table 14; 

 their corrosion rates in Table 15 and the effect of exposure on their 

 mechanical properties in Table 16. 



The silicon and silicon-molybdenum cast irons were uncorroded 



