RESULTS AND DISCUSSION 



The results presented and discussed herein also include the 

 corrosion data for titanium exposed on the STU structures for the 

 International Nickel Company, Incorporated as granted by Reference 8. 

 Results from other participants in the NCEL exposures are also in- 

 cluded; U. S. Navy Marine Engineering Laboratory (Reference 9), the 

 Chemistry Division, NCEL (Reference 10), and U. S. Naval Air 

 Engineering Center (Reference 11). Deep ocean data from the 

 Atlantic Ocean (TOTO) are also included for purposes of comparison; 

 Naval Research Laboratory (Reference 12) and Naval Applied Science 

 Laboratory (Reference 13). 



The chemical compositions of the titanium alloys are given in 

 Table 2, their corrosion rates in Table 3, their stress corrosion 

 behavior in Table 4 and the effect of corrosion on their mechanical 

 properties in Table 5. 



Corrosion 



There was no corrosion of any of the alloys at the surface or 

 at either nominal depth (2,500 or 6,000 feet) for any period of 

 exposure except two alloys; the Navy Marine Engineering Laboratory 

 reported a corrosion rate of 0.19 MPY for unalloyed titanium and 

 of 0.18 MPY for the 6 A1-4V alloy after 123 days of exposure at a 

 depth of 5,640 feet in the Pacific Ocean, Reference 9. They also 

 reported no visible corrosion. For practical purposes, these values 

 are considered to be inconsequential. 



Alloys 75A, Ti-0.15 Pd, 5Al-2.5Sn, 6A1-4V and 13V-llCr-3Al were 

 fusion welded by the inert-gas shielded arc, non-consumable (tungsten- 

 arc) electrode process (TIG). There were transverse butt welds and 

 3-inch diameter circular welds in the 6 inch by 12 inch specimens. 

 The welding stresses of these specimens were not relieved by an 

 annealing treatment in order to simulate a welded component not 

 adaptable to stress relieving after welding. There was no visible 

 corrosion of these welded alloys except for stress corrosion crack- 

 ing of the 13V-llCr-3Al alloy with the circular welds. This will 

 be discuss under stress corrosion. 



The 6A1-4V alloy was also exposed as: 



a. Wire, 0.020, 0.045 and 0.063 inch diameter 



b. Cables, 1/16"- 1 x 19, %" - 6 x 19, %" - 6 x 19 with Type 

 304 stainless steel swaged ends and %" - 6 x 19 tied with mild steel 

 wire. 



