seawater. The corrosion rates of Ni-Cr-Fe X750, Ni-Mo 2, Ni-200 and 

 Ni-Cu 402, 406, 410, K500, K505 and 45-55 alloys decreased linearly 

 with the concentration of oxygen in seawater. 



The corrosion rates of Ni-200, Ni-Cu 400, Ni-Cr-Fe 600 and X750, 

 and Ni-Fe-Cr 902 decreased with increasing time of exposure at the 

 surface. 



In general, pitting and crevice corrosion were more rapid in sur- 

 face seawater exposure than at depth. 



There was either no corrosion or uniform corrosion of weld beads and 

 in the adjacent heat affected zones when Ni-Cu 400 alloy was welded 

 with electrodes 130 and 180, Ni-Cr-Fe 718 with electrode 718, and Ni- 

 Cr-Mo 625 with electrode 625. 



There was selective corrosion, line corrosion or pitting of either 

 the weld beads or in the adjacent heat affected zones or both when Ni- 

 200 was welded with electrodes 61 and 141, Ni-Cu 400 with electrodes 60 

 and 190, Ni-Cu K500 with electrodes 64 and 134, Ni-Cr-Fe 600 with elec- 

 trodes 62, 82, 132 and 182, Ni-Cr-Fe X750 with electrodes 69 and 718, 

 Ni-Fe-Cr 800 with electrodes 82 and 138, and Ni-Fe-Cr 825 with elec- 

 trodes 65 and 135. 



Steels 



The steels were all corroded uniformly and their corrosion rates 

 were comparable - carbon steels, low alloy-high strength steels, nickel 

 steels, and the very high strength steels. 



The corrosion rates of the steels were lower at depth than at the 

 surface, but they did not decrease progressively with increasing depth; 

 i.e., they were not depth dependent. 



The average corrosion rates of all the steels decreased linearly 

 with the concentration of oxygen in seawater. 



The corrosion rates, the oxygen concentration and temperature of 

 seawater were analyzed using linear regression analysis. The follow- 

 ing relationships were obtained for AISI 1010 steel and the averages 

 of the other steels: 



Corrosion Rate (MPY) = 0.84 + 1.0 (0 2 ) + 0.014 (T) 



(Avg of carbon and 

 low alloy steels) 



Corrosion Rate (MPY) = 0.19 + 1.1 (0 2 ) +0.1 (T) 



(AISI 1010) 



The corrosion rates are in mils per year (MPY) , the oxygen content 

 of seawater in milliliters per liter (ml/1) and temperature in degrees 

 Centigrade (°C). 



13 



