6,000 feet in the Pacific Ocean after 6 months of exposure, Reference 

 14. The oxygen concentration of the seawater at a depth of 5,600 feet 

 in the Atlantic was about the same as that at the surface in both the 

 Atlantic and Pacific Oceans, which could be the reason for the rapid 

 rate of pitting. Its performance at the 5,600-foot depth in the Atlan- 

 tic is comparable with the performance of AISI Type 202 after 6 months 

 of exposure at the surface in the Pacific where the oxygen concentra- 

 tions were about the same. 



AISI Type 201 stainless steel was much more resistant to corrosion 

 by seawater at the surface and at depth than was AISI 202. 



AISI Type 300 Series Stainless Steels 



The AISI Type 300 stainless steels are those which contain a mini- 

 mum of 16 percent chromium and 6 percent nickel and are classed as 

 austenitic. 



The corrosion rates, maximum pit depths, maximum lengths of tunnel 

 corrosion, depths of crevice corrosion and types of corrosion are given 

 in Table 4 and all except the types of corrosion and tunnel corrosion 

 are shown graphically in Figures 8 through 23. 



Corrosion of AISI Type 301 stainless steel was predominately of 

 the pitting and tunneling types, Figure 8. The 103-mil thick specimens 

 were perforated by pitting and tunneling within 6 months of exposure in 

 seawater at the surface and by tunneling within 6 months of exposure at 

 both the 2,500- and 6,000-foot depths. The bottom sediments at the 

 2,500- and 6,000-foot depths were about as corrosive as the seawater 

 above. 



AISI Type 302 stainless steel, Figure 9, was perforated by pitting 

 and tunneling corrosion within 6 months at the surface and by pitting, 

 tunneling and crevice corrosion within the same period of exposure at 

 the 2,500-foot depth. Only crevice corrosion was significant at the 

 6,000-foot depth after longer than 6 months of exposure except that the 

 alloy was perforated by tunnel corrosion after 751 days in the bottom 

 sediment and the longest tunnel was 6 inches. The bottom sediments 

 generally were no more aggressive than the seawater above. Crevice and 

 tunneling corrosion were more prevalent than was the pitting type of 

 corrosion. 



Forgeson, Southwell and Alexander, Reference 15, reported that AISI 

 Type 302 stainless steel was perforated (261 mils) within 1 year when 

 exposed in surface seawater in the Pacific Ocean at Fort Amador, Panama 

 Canal Zone. This corrosion attack was considerably more rapid than at 

 both the 2,500- and 6,000-foot depths and at the surface at Port 

 Hueneme for the same period of exposure. It is attributed to the dif- 

 ferences in oxygen contents of the seawater and to differences in 

 temperature. 



The pitting and tunneling types of corrosion were more severe in 

 AISI Type 304 stainless steel than was crevice corrosion, Figure 10. 



