not progressively. The maximum pit depths of 5083-H113 were apparently 

 not dependent upon the oxygen concentration. 



The corrosion rates of the 5000 Series aluminum alloys and 6061-T6 

 decreased with increasing time of exposure at the surface in the Pacific 

 Ocean while their maximum pit depths increased. The corrosion rates 

 of 2219-T81, 3003-H14 and Alclad 3003-H12 decreased with time of exposure 

 at the surface through 540 days of exposure and thereafter, for some un- 

 known reason, increased rapidly. Their maximum pit depths, in general, 

 increased with time of exposure. 



The aluminum alloys were attacked by pitting and crevice types of 

 corrosion; hence, corrosion rates calculated from weight losses are un- 

 suitable for assessing the corrosion behavior. 



Crevice corrosion, in general, was more severe at depth than at 

 the surface. 



Copper Alloys 



The copper alloys, in general, corroded uniformly except for some 

 isolated cases of pitting and cratering. Also, there was dezincifica- 

 tion of Muntz metal and nickel-manganese bronze and dealuminifi cation 

 of the aluminum bronzes. 



The corrosion rate of copper was essentially unaffected by depth 

 and that of all the copper alloys was lower at depth than at the sur- 

 face, but not progressively. 



The corrosion rate of copper was unaffected by changes in the con- 

 centration of oxygen in seawater while the average rate of the copper 

 alloys decreased with decreasing concentration of oxygen. The corro- 

 sion rate of Muntz metal, which also was dezincified, also decreased 

 with the concentration of oxygen in seawater. 



The corrosion rates of all the copper alloys decreased with in- 

 creasing time of exposure at the surface except Muntz metal whose cor- 

 rosion rate increased with time. 



Nickel Alloys 



Fourteen (14) of the nickel base alloys were uncorroded: Ni-Cr- 

 Fe 718, Ni-Cr-Mo 3, Ni-Cr-Mo 625, Ni-Fe-Cr 800, Ni-Fe-Cr 804, Ni-Fe-Cr 

 825, Ni-Fe-Cr 825 (sensitized), Ni-Fe-Cr 825Cb, Ni-Fe-Cr 901, Ni-Cr- 

 Fe-Mo "F", Ni-Cr-Fe-Mo "G", Ni-Cr-Fe-Mo "X" , Ni-Mo-Fe "B", and Ni-Mo- 

 Cr "C". 



The corrosion rates of the other nickel base alloys were higher at 

 the surface than at depth. The corrosion rates of Ni-Cr-Fe 600 and Ni- 

 Cr-Fe 88 decreased with increasing depth while those of the other alloys 

 did not decrease progressively with depth. 



Most of the alloys which were corroded were also attacked by crev- 

 ice corrosion. 



The corrosion rates of all except two nickel base alloys (Ni-Sn- 

 Zn 23 and Ni-Si D) decreased with decreasing concentration of oxygen in 



12 



