These derived formulae illustrate two important points: 



(1) The concentration of oxygen in seawater is a major vari- 

 able and its effect on the corrosion rate of steel in seawater is linear. 



(2) The temperature of seawater has less effect on the corro- 

 sion of steel in seawater than the oxygen content and its effect is also 

 linear. 



These formulae, however, cannot be used to predict the corrosion 

 rates of steels in seawater at other locations due to the influence of 

 other variables such as time, currents, sediment effects, etc. 



The corrosion rates of the steels decreased progressively with in- 

 creasing time of exposure in surface seawater. 



Cast Irons 



Silicon and silicon-molybdenum cast irons were uncorroded in sea- 

 water at the surface and at depth in the Pacific Ocean after one year 

 of exposure. 



The corrosion rates of the other cast irons were lower at depth 

 than at the surface, but were not depth dependent. 



The corrosion rates of the alloy cast irons and gray cast iron 

 decreased linearly with the concentration of oxygen in seawater and 

 those of the austenitic cast irons progressively. 



The corrosion rates of two austenitic cast irons, Type 4 and Type 

 D-2C, decreased asymptotically with time of exposure at the surface in 

 seawater. 



Stainless Steels 



The following stainless steels were attacked only by incipient 

 crevice corrosion after one year of exposure in seawater: AISI Type 

 309, 316L, 317, 329 and 633, 20Cb3 and Ni-Cr-Mo-Si. 



All the other stainless steels were attacked by pitting, tunneling 

 and crevice corrosion in various degrees of severity. 



In general, the miscellaneous wrought and cast stainless steels, 

 except the 18C-14Mn-0 . 5N steel, were less severely attacked than the 

 others . 



Titanium Alloys 



The titanium alloys, unwelded and welded, except the 13V-llCr-3Al 

 alloy, were uncorroded. Welded 13V-llCr-3Al titanium alloy was suscep- 

 tible to stress corrosion cracking when the welding stresses were not 

 relieved by thermal treatment. 



14 



