Stress Corrosion 



Two copper-zinc alloys, arsenical admiralty and Muntz metal were 

 exposed while stressed at values equivalent to 50 and 75 percent of 

 their respective yield strengths, as shown in Table 8. They were 

 immune to stress corrosion cracking for 403 days of exposure at a depth 

 of 6,000 feet and 402 days of exposure at a depth of 2,500 feet. 



Mechanical Properties 



The effect of corrosion on the mechanical properties of three 

 copper-zinc alloys, arsenical admiralty, Muntz metal and nickel- 

 manganese bronze are given in Table 9 and shown graphically in Figures 

 19, 20, and 21, 



The mechanical properties of arsenical admiralty were not im- 

 paired. Figure 19, while those of Muntz metal, Figure 20, and nickel- 

 manganese bronze. Figure 21, were impaired. In both alloys, the im- 

 pairment increased with time of exposure at both depths, 2,500 and 

 6,000 feet. The degree of impairment in both cases roughly paralleled 

 the severity of the dezincif ication. 



Corrosion Products 



The corrosion products which formed on cast nickel-manganese bronze 

 during 403 days of exposure at a depth of 6,000 feet were analyzed by 

 X-ray diffraction, spectrographic , Infra-red spectrophotometer and 

 quantitative analyses methods. The corrosion products were composed of 

 cupric chloride (CuCl2*2H20) ; copper hydroxychloride (Cu2(0H)3Cl) ; 

 copper as metal 35.987o; minor amounts of aluminum, iron, silicon, and 

 sodium; chloride ions as CI, 0.917o; sulfate ions as SO4, ll,537o; small 

 quantities of an organic compound or compounds present due to decom- 

 posed algae and vegetative materials. 



BRONZES 



The chemical compositions of the bronzes are given in Table 10, 

 their corrosion rates and types of corrosion in Table 11, their resis- 

 tance to stress corrosion cracking in Table 12 and the effect of ex- 

 posure in the sea water on their mechanical properties in Table 13. 



Corrosion 



The corrosion rates of G bronze and modified G bronze are shown 

 in Figure 22. At the 6,000 foot depth, from 123 to 1064 days of 

 exposure, they corroded at essentially the same rate both in the sea 

 water and when partially embedded in the bottom sediments. Their 



