circular welds in Ni-Cu 400 alloy by the manual 

 shielded metal-arc process with electrode 190 cor- 

 roded uniformly both in the seawater and in the 

 bottom sediment after 189 days of exposure at a 

 depth of 5,900 feet. The unrelieved circular welds 

 were tested to determine whether welding stresses 

 would cause any corrosion-induced cracking. When 

 Ni-Cu 400 alloy was welded by the manual shielded 

 metal-arc process with electrodes 1 30 and 180, the 

 weld beads were corroded uniformly after 181 days 

 of exposure at the surface and after 402 days of 

 exposure at the 2,500-foot depth. There was no 

 preferential corrosion when Ni-Cu 400 was TIG 

 welded with electrode 167 after 402 days of exposure 

 at the 2,500-foot depth, but the weld bead was 

 selectively attacked and was covered with a deposit of 

 copper after 403 days of exposure at the 6,000-foot 

 depth [7j. 



The weld beads in Ni-Cu K-500 alloy made by the 

 manual shielded metal-arc process with electrode 134 

 were attacked by pitting corrosion of the weld bead 

 and the heat-affected zone after 181 days of exposure 

 at the surface, by crater corrosion of the weld bead 

 after 540 days of exposure at the surface, and by line 

 corrosion at the edge of the weld bead after 402 days 

 of exposure at the 2,500-foot depth. When Ni-Cu 

 K-500 alloy was TIG welded with filler metal 64, the 

 weld beads were uniformly corroded after 181 days 

 of exposure at the surface and 402 days of exposure 

 at the 2,500-foot depth, and the weld beads and the 

 heat-affected zones were attacked by pitting cor- 

 rosion after 540 days of exposure at the surface. 



4.2.5. Galvanic Corrosion 



When AISI 4130 steel was fastened to Ni-Cu 400 

 alloy in a surface area ratio of 1:2, the AISI 4130 was 

 severely corroded and the Ni-Cu 400 was uncorroded 

 after 403 days of exposure at the 6,000-foot depth 

 [7] . This shows that the steel was being sacrificed to 

 protect the nickel- copper alloy. 



4.2.6. Crevice Corrosion 



4.2.7. Corrosion Products 



X-ray diffraction, spectrochemical, and chemical 

 analyses of corrosion products removed from nickel- 

 copper alloys 400 and K-500 showed that they were 

 composed of cupric oxide (CuO), nickel oxide (NiO), 

 nickel hydroxide (Ni(OH) 2 ), cupric chloride (CuCl 2 ), 

 copper- oxy-chloride (CuCl 2 ;3CuO;4H 2 0), a trace of 

 nickel sulfide (NiS), and phosphate, chloride, and 

 sulfate ions. 



4.2.8. Mechanical Properties 



The effects of exposure on the mechanical pro- 

 perties of Ni-Cu 400 and K-500 alloys are shown in 

 Table 31. There were no significant changes due to 

 corrosion of either unwelded or welded alloys. 



4.3. NICKEL ALLOYS 



The chemical compositions of the nickel alloys 

 are given in Table 32, their corrosion rates and types 

 of corrosion in Table 33, and the changes in their 

 mechanical properties due to corrosion in Table 34. 



There were no significant weight losses (none 

 greater than 0.1 mpy) or any visible corrosion on any 

 of the following alloys: 



Ni-Cr-Fe 718, unwelded and welded 



Ni-Cr-Mo 625, unwelded and welded 



Ni-Mo-Cr C and 3 



Ni-Cr-Fe-Mo F and G 



Ni-Cr-Co 41 



There were no significant weight losses (none 

 greater than 0.1 mpy) and only some cases of 

 incipient crevice corrosion on the following alloys: 



Ni-Fe-Cr804, 825Cb, and 901 



Ni-Co-Cr700 



Ni-Cr-Fe-Mo X 



Ni-Cu 400 alloy hardware was attacked by crevice The corrosion resistance of Ni-Fe-Cr 825Cb was 



corrosion after 751 days of exposure at the better than that of its counterparts 825 and 825S 



6,000-foot depth when in contact with fiberglass (sensitized). Alloy 825 was attacked by both pitting 



[13] . and crevice corrosion, and 82 5S had only one case of 



91 



