Welded AISI Type 633-RH1100 specimens were perforated by tunneling 

 type of pitting corrosion within 6 months of exposure at the surface 

 and at the 2, 500- foot depth, Figure 31. After 1 year of exposure at 

 the surface and at the 6,000-foot depth they were also perforated by 

 crevice corrosion. The weld beads were unattacked except after 1 year 

 of exposure in the bottom sediment, at the 2,500-foot depth where the 

 butt welded specimen was perforated by tunneling corrosion in the heat 

 affected zone and the circular weld specimen failed by stress corrosion 

 cracking. 



AISI Type 633 stainless steel was attacked only by incipient crevice 

 corrosion at the surface and at both depths except that it was 1 mil 

 deep after 1064 days of exposure in the bottom sediment, Figure 19. 



Crevice and incipient pitting were the manifestations of corrosion 

 on AISI Type 634-CRT stainless steel, Figure 32. Crevice corrosion was 

 most severe after 1 year of exposure at depth of 2,500 and 6,000 feet. 



Corrosion of the crevice, tunneling and pitting types were more 

 severe and rapid at the surface than at depth for AISI Type 635 stain- 

 less steel, Figure 33. The specimens were perforated by crevice corro- 

 sion within 6 months of exposure at the surface but not until after 1 

 year of exposure at the 2,500-foot depth. 



Except for pitting to a maximum depth of 3 mils after 6 months of 

 exposure at the surface, a precipitation hardening stainless steel con- 

 taining 17Cr-14Ni-3Cu-2Mo was attacked by incipient crevice corrosion 

 after longer periods of exposure both at the surface and at depth, 

 Figure 34. 



The rates of pitting and of tunneling attack on welded stainless 

 steel Phl4-8Mo-SRH950 was greater in surface seawater than at either 

 depth for equivalent periods of exposure, Figure 35. Pitting and tun- 

 neling corrosion were more prevalent than crevice corrosion. Pitting 

 corrosion perforated the weld bead in one specimen after 6 months of 

 exposure at the surface and the heat affected zone adjacent to the weld 

 bead after 1 year at the 6,000-foot depth. 



Precipitation hardening stainless steel 15-7AMV in three heat- 

 treated (aged) conditions; annealed, RH1150 and RH950 corroded at ex- 

 tremely rapid rates by crevice, pitting, tunneling and edge corrosion 

 as shown in Figures 36, 37 and 38. In many instances, large portions 

 of the specimens had been consumed by corrosion; in other cases tun- 

 neling corrosion had progressed for 11 of the 12-inch length of the 

 specimens within a year's time. 



The 15-7AMV precipitation hardening stainless steels were more 

 susceptible to corrosion than the others. 



In general the corrosion resistance of the precipitation hardening 

 stainless steels was less than that of the 200, 300 and 400 Series 

 stainless steels. 



Miscellaneous Stainless Steels 



Included in this category are cast, specialty and modified 

 stainless steels. 



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