This report presents a discussion of the results of the corrosion 
of aluminum and nickel alloys, steels, stainless steels, and titanium 
alloys after 189 days of exposure at a depth of 5,900 feet, STU I-5, 
Table 1. 
RESULTS AND DISCUSSIONS 
Aluminum Alloys 
The chemical compositions of the aluminum alloys are given in 
Table 2 and their corrosion rates and types of corrosion in Table 3. 
Since the aluminum alloys corroded chiefly by pitting and crevice 
corrosion, the corrosion rates calculated from weight losses in Table 
3 are meaningless. A good illustration of this is 6061-T6 where the 
calculated corrosion rates are 0.1 MPY in both the water and the bottom 
sediments, but the maximum and average pit depths are more than 10 times 
greater in the bottom sediments than in seawater, and crevice corrosion 
was very evident in the bottom sediments contrasted to none in the 
seawater. 
For most aluminum alloys pitting and crevice corrosion were more 
severe in the bottom sediments than in the seawater. Also, pitting 
and crevice corrosion were more severe at depths than at the surface 
for the same period of exposure as is shown by comparing the data in 
Table 3 of Reference 11 with Table 3 of this report. 
Pitting corrosion was more localized in the heat affected zones 
adjacent to the weld beads in alloys 5083-H113 and 7039-T64 than in 
the plate materials unaffected by the heat of welding. 
Nickel Alloys 
The chemical compositions of the nickel alloys are given in Table 
4 and their corrosion rates and types of corrosion in Table 5. 
In general, the corrosion rates of the nickel alloys in seawater 
and in the bottom sediments were comparable. There was pitting corro- 
sion only in the Ni-Cu alloys 400 and K-500 -- that in the K-500 alloy 
being much more severe than that in the 400 alloy. There was crevice 
corrosion in three alloys, Ni-Cu alloys 400 and K500, and in Ni-Cr-Fe 
600 alloy. Crevice corrosion was most severe in the Ni-Cr-Fe 600 al- 
loy. There was no significant corrosion of the other three alloys, 
Ni-Cr-Fe 718, Ni-Cr-Mo 625 and Ni-Fe-Cr 825. There was incipient pit-— 
ting or etching of the weld beads on Ni-Cu 400, Ni-Cr-Fe 718 and Ni-Fe- 
Cr 825 alloys. 
Comparison of the corrosion performance of the alloys in Table 5 
with companion alloys in Table 9 of Reference 11 shows that: (1) The 
performance of Ni-Cr-Fe 718 and Ni-Cr-Mo 625 alloys were the same; (2) 
crevice corrosion occurred in Ni-Fe-Cr 825 alloy at the surface in 
