Type 330 stainless steel contains 15% Cr-35% Ni. This alloy was 

 developed with such a high nickel content chiefly for high temperature 

 applications. Type 330 was perforated (50 mils) by both pitting and 

 crevice corrosion during exposure for 181 days in surface seawater. 

 It was free from pitting at depth in seawater but was attacked by 

 crevice corrosion varying from none to perforation. 



The least corroded 300 Series alloys were Types 317 and 329 on 

 which only incipient crevice corrosion (less than 1 mil deep) was 

 observed after 366 days of exposure in surface sea water, after 402 

 days of exposure at the 2,500-foot depth, and after 1,064 days of 

 exposure at the 6,000-foot depth, both in seawater and in the bottom 

 sediments. 



Sensitization (heating for 1 hour at 1200°F and cooling in air) 

 rendered AISI Types 304 and 316 more susceptible, particularly to 

 crevice corrosion, than their unsensitized counterparts. 



Series 400 Stainless Steels (12%-30% Cr) 



The straight chromium stainless steels, except AISI Type 446, 

 were corroded at faster rates in seawater at the surface and at depths 

 of 2,500 and 6,000 feet than were the 300 Series stainless steels. 

 Type 446 was perforated (50 mils) by both pitting and crevice corro- 

 sion during 182 days of exposure in surface seawater, while there was 

 no pitting, and crevice corrosion varied from none to 2 mils deep in 

 seawater at depth. 



Series 600 Stainless Steels (Precipitation Hardening) 



Precipitation hardening staineless steels AISI Types 630, 631, 

 632 and 635, PH14-8Mo and 15-7AMV were severely attacked by the pit- 

 ting, tunneling and crevice types of corrosion. The 15-7AMV was the 

 most severely corroded of these types; portions of many of the speci- 

 mens were missing because of the tunnel type of corrosion. In con- 

 trast to this (similar to the behavior of stainless steels of the 200 

 and 300 Series), Type 633 (17% Cr-4% Ni-3% Mo) precipitation harden- 

 ing stainless steel was attacked only by crevice corrosion to a max- 

 imum depth of 1 mil during 1,064 days of exposure in the bottom sedi- 

 ment at a depth of 6,000 feet. 



Miscellaneous Wrought and Cast Stainless Steels 



A cast alloy (Ni-Cr-Mo-Si) was uncorroded in seawater both at the 

 surface and at depth. Another cast alloy (RL-35-100) was corroded 

 only by general surface attack and cast alloy (Ni-Cr-Mo) was attacked 

 only by incipient crevice corrosion in all three seawater environments. 



There were isolated cases of pitting (14 mils) and crevice 

 corrosion (to 102 mils) on wrought alloy 20Cb while there was only 



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