after 200 days of exposure the corrosion rate was the same as at the 

 6,000 foot depth in the Pacific Ocean, The absence of any dezincifi- 

 cation of arsenical admiralty is attributed to the slight amount of 

 arsenic added to this alloy. It corroded at a higher rate at the sur- 

 face in the Pacific Ocean than at depth as shown in Figure 8. 



The corrosion of Muntz Metal at the 6,000 foot depth was erratic 

 as shown in Figure 9. This is attributed to the dezincif ication of the 

 alloy. The corrosion rates at the 2,500 foot depth were essentially 

 constant with time and those in the bottom sediments were lower than 

 those in the sea water. Muntz metal corroded at a higher rate at the 

 surface in the Pacific Ocean than at either depth and at the Panama 

 Canal Zone. Even though Muntz metal was dezincif ied during exposure at 

 the surface in the Pacific Ocean, Fort Amador, Panama Canal Zone, 

 Reference 16, its corrosion rate decreased asymptotically with time and 

 was lower than at the 6,000 foot depth. Muntz metal suffered from de- 

 zincif ication at the surface and at both depths in the Pacific Ocean, 

 the extent varying from slight to severe. The severity of the dezinci- 

 f ication after 751 days of exposure at a depth of 6,000 feet is shown 

 in Figure 10, the thickness of the specimen was reduced by 28 percent. 

 The dark bands on the edges are dezincif ied areas. 



Naval brass. Figure 11, corroded at a slower rate in sea water at 

 the 6,000 foot depth in the Pacific Ocean than at a depth of 5,600 feet 

 in the Atlantic Ocean, Reference 12, at the surface in the Pacific 

 Ocean at Fort Amador, Panama Canal Zone, Reference 16, and at Port 

 Hueneme Harbor, California, Reference 15, However, after 1050 days of 

 exposure at 5,600 feet in the Atlantic Ocean and 1064 days of exposure 

 at 6,000 feet in the Pacific Ocean the corrosion rates of Naval brass 

 were essentially the same. The corrosion rates at both surface loc- 

 ations and at the 6,000 foot depth decreased and became asymptotic 

 with time even though the rates were different. The differences in the 

 rates can be attributed at least partially to differences in the tem- 

 peratures at the three sites. The Naval brass was reported to have been 

 dezincified at the Panama Canal Zone but no dezincif ication was report- 

 ed at the surface at Port Hueneme or at depth in the Atlantic and 

 Pacific Oceans, Dezincif ication could be an additional cause (in 

 addition to temperature) for the higher corrosion rate at the Panama 

 Canal Zone. 



Manganese bronze. Figure 12, behaved similarly to Muntz metal. 

 Figure 9, in that it corroded erratically at the 6,000 foot depth which 

 is attributed to dezincif ication. At the 2,500 foot depth, the 

 corrosion rates decreased slightly with increasing time of exposure and 

 in the bottom sediment were lower than in the sea water. The corrosion 

 rate of manganese bronze at the surface of the Pacific Ocean at NCEL 

 was considerably higher than at either depth as well as at other loc- 

 ations. It was also severely dezincified. The corrosion rate of man- 

 ganese bronze decreased asymptotically with time at the surface in the 

 Pacific Ocean, Fort Amador, Panama Canal Zone, Reference 16, and was 

 constant with time between one and two and a half years of exposure in 



