the surface. The aggressiveness of the bottom sediments was the same 

 as the seawater at depth. 



The pitting and tunneling types of corrosion were more severe on 

 the AISI Type 316 stainless steel than was crevice corrosion although 

 the incidence of crevice corrosion was greater, Figure 16. The pitting 

 corrosion was also associated with the tunneling type of corrosion with 

 the tunnels being longer in the surface exposures. The intensity of 

 the pitting corrosion is indicated by the fact that the 230-mil thick 

 specimens were perforated within 181 days of exposure at the surface 

 and after 402 days of exposure at the 2,500-foot depth. Pitting corro- 

 sion was slightly worse in the seawater at depth than in the bottom 

 sediments but the reverse was found for crevice corrosion. 



The corrosion of AISI Type 316 stainless steel at the 6,000-foot 

 depth in the Pacific Ocean after 1064 days of exposure was slightly 

 faster than at the 5,600-foot depth in the Tongue-of-the-Ocean after 

 1050 days of exposure; Brown, et al. , Reference 14, reported no pitting 

 or crevice corrosion in the Tongue-of-the-Ocean while the maximum pit 

 depth in the Pacific was 21 mils and crevice corrosion was 1 mil. 



Forgeson, et al. , Reference 15, reported perforation by pitting 

 (245 mils) of AISI Type 316 stainless steel after 1 year of exposure in 

 surface seawater in the Pacific Ocean at Fort Amador, Panama Canal Zone. 

 Specimens 230 mils thick were perforated both by pitting and tunneling 

 within 6 months exposure in seawater at the surface at Port Hueneme. 

 With a higher water temperature at Fort Amador than at Port Hueneme one 

 would expect more rapid corrosion at Fort Amador. The faster corrosion 

 at Port Hueneme indicates that other variables have an effect, at least 

 in the case of stainless steel. 



Sensitization (heated 1 hour at 1200°F and cooled in air) rendered 

 AISI Type 316 stainless steel more susceptible to corrosion, (crevice 

 corrosion particularly) than the unsensitized steel, as shown by com- 

 parison of Figures 16 and 17. Crevice corrosion ranged from incipient 

 to perforation of the 50-mil thick specimens after 1 year in seawater 

 at the surface and after 2 years at the 6,000-foot depth both in sea- 

 water and the bottom sediment. The bottom sediments were about the same 

 as seawater at depth with regard to crevice corrosion but were less 

 aggressive with regard to pitting corrosion. 



The corrosion of AISI Type 316L (the low-carbon version of AISI 

 Type 316) stainless steel, Figure 18, is comparable with that of AISI 

 Type 316 stainless steel even though crevice corrosion was more frequent 

 and pitting and tunneling corrosion were less frequent than on the Type 

 316. Corrosion in the bottom sediments was about the same as in the 

 seawater above them. 



AISI Types 317 and 329 stainless steels were attacked only by 

 incipient crevice corrosion when exposed in seawater at the surface and 

 at a depth of 2,500 feet for 1 year and when exposed at a depth of 6,000 

 feet for 3 years, Figure 19. The same was true for the bottom sediments. 



There was no pitting corrosion of AISI Type 321 stainless steel in 

 seawater except to a depth of 22 mils after 1 year of surface exposure, 



