The maximum depths of pits in aluminum alloys 3003-H14 and 5083- 

 H113 were independent of the concentration of oxygen in seawater, Figure 

 7. The maximum pit depths of these two alloys were depth (pressure) 

 dependent as shown in Figure 5 . 



The corrosion rates of 6061-T6 and the 5000 series alloys (5083, 

 5086 and 5456) decreased with increasing time of exposure in surface 

 seawater while their maximum pit depths increased with time of exposure 

 as shown in Figure 8. The corrosion rates of alloys 3003-H14, Alclad 

 3003-H12 and 2219-T81 did not decrease constantly with increasing time 

 of exposure in surface seawater; they decreased with time through 540 

 days of exposure and thereafter increased sharply as shown in Figure 9. 



The depths of the maximum pits in alloy 2219-T81 increased with 

 time of exposure, those in alloy 3003-H14 decreased initially and after 

 400 days increased rapidly, Figure 9. The depths of the maximum pits 

 in Alclad 3003-H12 increased through the first 400 days of exposure 

 and thereafter became constant with time. This constancy is explained 

 by the fact that the sacrificial protective alloy layers on the Alclad 

 3003-H12 are corroded laterally, thus preventing pitting of the protec- 

 ted core alloy. 



The corrosion rates as well as the maximum pit depths of 6061-T6 

 and 2219-T81 increased with decreasing concentration of oxygen in sea- 

 water, Figures 3 and 6. However, both the corrosion rates and maximum 

 pit depths of 5086-H34 decreased with the concentration of oxygen in 

 seawater. Although the maximum pit depths of 2024-0 increased with 

 decreasing concentration of oxygen in seawater, Figure 6, its corrosion 

 rate appears to be affected to a much lesser extent by changes in the 

 concentration of oxygen in seawater, Figure 4. Neither the changes in 

 the corrosion rates nor the maximum pit depths of aluminum alloys 3003- 

 H14 and 5083-H113 appear to be dependent upon the changes in the concen- 

 tration of oxygen in seawater as shown in Figures 4 and 7. They are 

 generally greater at the lower concentrations of oxygen, although not 

 progressively. The corrosion rates of aluminum alloys 1100-H14, 3003- 

 H14 and 5083-H113 were depth (pressure) dependent in that they increased 

 with depth, Figure 2, while those of 5086-H34 alloy decreased slightly 

 with increasing depth. The corrosion rates of aluminum alloys 6061-T6, 

 2024-0 and 2219-T81 were not consistently influenced by depth, Figure 2. 

 The maximum pit depths of four alloys, 5083-H113, 2024-0, 5086-H34 and 

 3003-H14 appear to have been affected by depth; those of 5083-H113, 

 2024-0 and 3003-H14 increased with depth while those of 5086-H34 de- 

 creased with increasing depth, Figure 5. The maximum pit depths of 

 alloys 2219-T81 and.6061-T6 were not consistently affected by depth 

 except that their maximum pit depths at a depth of 6,000 feet were 

 deeper than at the surface. In general, the corrosion rates of the 

 aluminum alloys decreased with increasing time of exposure in surface 

 seawater while the maximum depths of the pits increased with time of 

 exposure, Figures 8 and 9. 



