SUMMARY AND CONCLUSIONS 



The purpose of this investigation was to determine the effects of 

 deep ocean environments on the corrosion and stress corrosion of titanium 

 alloys. To accomplish this, 473 specimens of 10 alloys were exposed at 

 the surface for 181 days and at nominal depths of 2,500 and 6,000 feet 

 for periods of time varying from 123 to 1064 days. 



There was no visible corrosion nor any significant weight losses of 

 any of the alloys after 181 days of exposure at the surface, 197 and 402 

 days at a nominal depth of 2,500 feet, and 123, 403, 751, and 1064 days 

 at a nominal depth of 6,000 feet either in the sea water or the bottom 

 sediment. 



Alloys, unwelded and with transverse butt welds, were not sus- 

 ceptible to stress corrosion cracking when stressed at values equivalent 

 to 75 percent of their respective yield strengths after 180 days of 

 exposure at the surface, 402 days at a nominal depth of 2,500 feet, and 

 751 days of exposure at a nominal depth of 6,000 feet, except the butt 

 welded 13V-llCr-3Al alloy. This alloy failed by stress corrosion crack- 

 ing after 35, 77 and 105 days of exposure at the surface. Flash welded 

 rings of 6A1-4V alloy did not stress corrosion crack when stressed to 

 60,000 psi and exposed at a depth of 2,370 feet for 402 days. The 

 residual stresses induced in 13V-llCr-3Al alloy sheet by a 3-inch 

 diameter unrelieved weld were great enough to cause stress corrosion 

 cracking after 181 days of exposure at the surface, 403 days at 6,780 

 feet, and 402 days at 2,370 feet. The other alloys, 75A, Ti-0.15Pd, 

 5Al-2.5Sn, 7Al-2Cb-lTa, and 6A1-4V, similarly welded were not susceptible 

 to stress corrosion cracking either at the surface or at depth. 



The mechanical properties of the alloys were not adversely 

 affected by exposure in sea water at depth. 



Differences in temperature, oxygen concentration, pressure and 

 velocity of flow between the surface and depths in the Pacific Ocean 

 appear to have no influence on the corrosion behavior of titanium alloys. 



