lower at the lower oxygen concentrations than at the highest, did not 

 decrease progressively with the oxygen concentration. 



Here again, comparison of the corrosion rates with the severity of 

 the pitting, tunneling and crevice types of corrosion (Table 6) showed 

 no definite correlations. 



The corrosion rates and types of corrosion of the miscellaneous 

 cast and wrought stainless steels are given in Table 17. Except for 

 the 18Cr-14Mn-0 . 5N which contained no nickel, the others contained 

 greater percentages of chromium and nickel than the conventional stain- 

 less steels in addition to molybdenum and copper. The corrosion rates 

 of these stainless steels were mostly less than 0.1 MPY and instances 

 of pitting and crevice corrosion were few except for the 18Cr-15Mn-0.5N 

 alloy. Significant pitting and crevice corrosion occurred during sur- 

 face exposures of wrought alloy 20-Cb and cast alloy Ni-Cr-Cu-Mo #2. 



TITANIUM ALLOYS 



The chemical compositions of the titanium alloys are given in 

 Table 18 and their corrosion rates and types of corrosion in Table 19. 



There was no corrosion of any of the alloys except the welded 

 13V-llCr-3Al alloy. It was susceptible to stress corrosion cracking 

 during surface exposures. Specimens were in two welded conditions, 

 half were butt welded and a 3-inch diameter circular weld bead was 

 placed on the other half of the specimens. The welded specimens were 

 intentionally not stress relieved in order to retain the maximum in- 

 ternal welding stresses in the specimens during exposure. The stress 

 corrosion cracks extended across the butt welds normal to the direction 

 of the beads and developed within 398 days of exposure. The stress 

 corrosion cracks in the specimens with the circular welds extended 

 radially across the weld beads and they also developed within 398 days 

 of exposure. 



MISCELLANEOUS ALLOYS 



The chemical compositions of the miscellaneous alloys are given in 

 Table 20 and their corrosion rates and types of corrosion in Table 21. 

 The effect of depth, concentration of oxygen in seawater and time are 

 shown in Figures 32 to 34. 



Columbium, tantalum and tantalum alloy Ta60 were uncorroded during 

 763 days of exposure at the surface and 402 days of exposure at a depth 

 of 2,500 feet. 



The effect of depth on the corrosion rates of the miscellaneous 

 alloys is shown in Figure 32. The corrosion rates of tin, molybdenum 

 and tungsten decreased with increasing depth. The corrosion rates of 

 lead and lead-tin solder were lower at depth than at the surface but 



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