7 percent aluminum bronzes were about the same at the Panama Canal Zone 

 as at depth. 



The bronzes, except the aluminum bronzes, nickel-aluminum bronze 

 containing 10 percent aluminum and the silicon bronzes, were corroded 

 uniformly. These bronzes were attacked by selective corrosion whereby 

 either aluminum or silicon was selectively removed with a layer of 

 metallic copper remaining on the surfaces of the specimens. Where an 

 alloy is corroded by this type of attack, corrosion rates are not a 

 true indication of the amount of corrosion because the weight losses 

 are low due to the weight of redeposited copper remaining on the speci- 

 mens. Hence in these cases, corrosion rates are not reliable indi- 

 cations of corrosion damage. 



Phosphorous bronzes A and D, 7 percent aluminum bronze and silicon 

 bronze A were not susceptible to stress corrosion cracking at depths 

 of 2,500 and 6,000 feet in the Pacific Ocean. 



The mechanical properties of the phosphorous bronzes A and D were 

 not adversely affected by exposure at depth in the Pacific Ocean while 

 those of 7 percent aluminum bronze and silicon bronze A were adversely 

 affected. This adverse effect is attributed to the selective corrosion 

 of the 7 percent aluminum bronze and the silicon bronze A. 



Corrosion products were copper oxy-chloride (CuCl2'3CuO'4H20) and 

 cupric chloride (CUCI2). 



Copper-Nickel Alloys 



The corrosion rates of the copper-nickel alloys in sea water and 

 in the bottom sediments at both the 2,500 and 6,000 foot depths de- 

 creased with increasing duration of exposure. However, the corrosion 

 rates in the bottom sediments were lower than those in sea water. 

 Copper-nickel alloy, 70 percent copper-30 percent nickel containing 5 

 percent iron corroded at much lower rates in sea water at both depths 

 through 400 days of exposure than did the other alloys. These lower 

 corrosion rates are attributed to the protection afforded the alloy by 

 the hard, impervious film on its surface which did not start to deter- 

 iorate until after 400 days of exposure; thereafter, the corrosion 

 rates increased. The copper-nickel alloys, 70-30 containing 5 percent 

 iron, 80-20 and 55-45 corroded at faster rates at the surface in the 

 Pacific Ocean at Point Mugu than at either depth; those of 90-10 and 

 Cu-Ni-Zn-Pb alloys were the same at the surface and at depth; and those 

 of 70-30 containing 0,5 percent iron and nickel-silver were lower at 

 the surface than at depth. The 70-30 alloy with 0,5 percent iron cor- 

 roded at the same rate after 2 years of exposure at depth as it did at 

 the surface of the Pacific Ocean at the Panama Canal Zone, 



Copper-nickel alloys 95-5, 90-10, 80-20, 70-30 containing 0,5 per- 

 cent iron, nickel-silver and Cu-Ni-Zn-Pb corroded uniformly. The 70-30 

 alloy containing 5 percent iron was attacked by crevice and pitting 

 corrosion after 751 days of exposure at the 6,000 foot depth and the 



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