COPPER ALLOYS 



The chemical compositions of the copper alloys are given in Table 

 5, their corrosion rates in Table 6 and the effect of exposure on 

 their mechanical properties in Table 7. 



The corrosion rates of the majority of the alloys (28 of 33) were 

 higher for surface waters than at both depths, 2,500 and 6,000 feet. 

 The corrosion rates of nickel brass, 90-10 cupro-nickel (CDA706) and 

 nickel silver (CDA752) were higher for surface waters than at the 2,500 

 foot depth but were lower than at the 6,000 foot depth. The corrosion 

 rates of cast nickel-manganese bronze and 70-30 cupro-nickel containing 

 0.5 percent iron were lower at the surface than at both depths. 



The corrosion rates of most of the copper alloys increased as the 

 concentration of the dissolved oxygen of the sea water increased. The 

 average, maximum and minimum corrosion rates of 26 of the alloys are 

 plotted against the dissolved oxygen contents at the three depths 

 (Table 1) in Figure 4. The corrosion rates of nickel brass, leaded 

 tin bronze, 90-10 cupro-nickel, nickel silver and 55-45 cupro-nickel 

 decreased as the concentration of oxygen in the sea water decreased. 

 However, the corrosion rates of nickel brass, 90-10 cupro-nickel and 

 nickel silver were higher at the intermediate concentration of oxygen, 

 1.3 ml/1 (6,000 foot depth) than at the higher concentration of oxygen, 

 5.25 ml/1 (surface) while those of leaded tin bronze and 55-45 cupro- 

 nickel were lower at the intermediate concentration of oxygen than at 

 the higher concentration of oxygen. The corrosion rates of 70-30 

 cupro-nickel containing 0.5 percent iron and cast nickel-manganese 

 bronze increased with decreasing concentration of oxygen in sea water. 



Slight dezincif ication was found on red brass at the surface 

 whereas none was found at depth; dezincif ication of Muntz metal was 

 more severe at the surface than at depth; and dezincif ication of man- 

 ganese bronze A and cast nickel-manganese bronze were about the same 

 in severity at the surface as at depth. 



Aluminum bronze, 7%, CDA No. 614 was dealuminif ied at the surface, 

 slightly dealuminif ied at the 6,000 foot depth but there was no such 

 attack at the 2,500 foot depth. Aluminum bronze, 107» was moderately 

 dealuminif ied at the surface and at the 2,500 foot depth but only 

 slightly dealuminif ied at the 6,000 foot depth. Dealuminif ication 

 decreased from severe to moderate to very slight as the depth increased 

 in 137o aluminum bronze. 



Crevice corrosion was found on only three alloys, copper, nickel- 

 aluminum bronze No. 2 and 70-30 cupro-nickel with 57, iron at the sur- 

 face while none was encountered at depth. Pitting also was found at 

 the surface while none was found at depth on alloys, copper, P bronze 

 A, Ni-Vee bronzes A and B, and 70-30 cupro-nickel containing 5% iron. 



The percent change in the mechanical properties of the copper 

 base alloys after exposure are shown in Table 7. The mechanical pro- 

 perties were adversely affected slightly by exposure at the surface 



