The welded titanium alloys were exposed in the "as welded" con- 

 dition. That is, the stresses imposed in the specimens by the welding 

 operation were not relieved by annealing prior to exposure. The pro- 

 cess of placing a circular weld in a specimen imposes very high 

 residual stresses in the specimen. Such circular welds simulate multi- 

 axial stresses imposed in structures or parts fabricated by welding. 

 Unrelieved circular welds will cause stress corrosion cracking if the 

 residual stresses are high enough and if the environment is appropriate. 



The specimen of titanium alloy 13V-llCr-3Al with a circular weld 

 cracked radially across the weld during 181 days of exposure at the 

 surface of the sea water as shown in Figure 14, companion specimens 

 exposed at depths of 2,500 and 6,000 feet for comparable periods of 

 exposure did not fail by stress corrosion cracking. This indicates 

 that sea water at depths is not as aggressive for promoting stress 

 corrosion cracking of this alloy as is surface sea water. 



The effects of exposure in sea water on the mechanical properties 

 of titanium alloys are given in Table 22. The mechanical properties 

 were unaffected by exposure both at the surface and at depth in sea 

 water . 



MISCELLANEOUS ALLOYS 



The chemical compositions of the alloys are given in Table 23, 

 their corrosion rates in Table 24, and the effect of exposure in sur- 

 face sea water on the mechanical properties of some of the alloys in 

 Table 25. 



The corrosion rates and types of corrosion of the miscellaneous 

 alloys are given in Table 24. The iron-nickel- chromium-molybdenum 

 alloys, columbium, tantalum and Ta-60 alloy were uncorroded after 6 

 months of exposure. The iron-nickel-chromium alloys were attacked by 

 crevice corrosion to depths of from 18 to 20 mils at the surface but 

 were practically uncorroded at depths of 2,500 and 6,000 feet after 

 equivalent periods of exposure. 



Chemical lead, antimonial lead and tellurium lead corroded uniform- 

 ly with their corrosion rates being lower at the 2,500 foot depth than 

 at the surface and at the 6,000 foot depth. Chemical lead, in general, 

 was more corrosion resistant than the other two alloys. 



Magnesium alloy AZ31B was practically disintegrated within 6 months 

 of exposure both in surface sea water and at depths of 2,500 and 6,000 

 feet. 



Tin, zinc and lead-tin solder corroded at appreciable rates in sea 

 water, those at the surface being higher than those at depth except 

 zinc after 123 days at 6,000 feet. Tin and zinc were pitted while the 

 lead-tin solder corroded uniformly. 



Molybdenum and tungsten corroded at low rates and the type of 

 attack was uniform. 



The effects of exposure in surface sea water for 6 months on the 

 mechanical properties for some of the alloys are given in Table 25. 



