The Naval Applied Science Laboratory reported that nickel 200 

 was practically unattacked after 199 days of exposure at a depth of 

 4,500 feet in the Tongue-of ~the-Ocean (TOTO) , Atlantic Ocean. This 

 is in contrast to the results obtained in the Pacific Ocean where 

 the corrosion rates in the water were low at both depths; from less 

 than 0.1 to 0.7 MPY at 5,640 feet for 123 days and 0.5 MPY at 2,340 

 feet for 197 days, but there was crevice corrosion on nickel at both 

 depths. 



Although the Naval Research Laboratory reported concentration 

 cell and pitting (average depth, 125 to 143 mils) corrosion of nickel 

 200 in surface sea water at Fort Amador, Panama Canal Zone, Pacific 

 Ocean, the corrosion rate of nickel decreased with time of exposure 

 as shown in Figure 3. However, as also shown in Figure 3, the cor- 

 rosion rates of nickel 200 at a nominal depth of 6,000 feet in the 

 Pacific Ocean increased sharply with time of exposure to 2 years 

 and then decreased. After 2 years of exposure they are comparable 

 with those for surface sea waters at Fort Amador. As previously 

 emphasized, more weight must be given to concentration cell, crevice 

 and pitting types of corrosion as a basis for recommending nickels 

 for sea water applications than to corrosion rates calculated from 

 weight loss determinations. 



There was no definite correlation between corrosion rates of 

 most of the nickels at the nominal 6,000 foot depth and at the 

 nominal 2,500 foot depth. Only cast nickel-210 and nickel-301 cor- 

 roded at consistently slower rates at the 2,500 foot depth than at 

 the 6,000 foot depth both in the sea water and in the bottom sedi- 

 ments. At both depths these two nickels corroded at slower rates 

 in the bottom sediment than in the sea water. 



The nickel containing 4.5 percent aluminum (nickel 301) was 

 more susceptible to crevice corrosion than the other nickels. Cast 

 nickel (nickel 210) was less susceptible to crevice corrosion than 

 the other nickels but was attacked more by the pitting type of 

 corrosion. 



The weld beads were preferentially corroded after 402 days of 

 exposure at a depth of 2,370 feet in the sea water when nickel was 

 welded by the inert gas welding technique using filler metal 61 and 

 by the metal-arc welding technique using welding electrode 141. The 

 preferential corrosion of filler metal 61 is shown in Figure 4. How- 

 ever, in the bottom sediment the weld bead made with filler metal 61 

 was not preferentially corroded. 



Metallographic examinations of the weld materials and the ad- 

 jacent-heatr-af f ected-zones showed no evidence of selective corrosion 

 at grain boundaries. It is, therefore, concluded that the weld bead 



