zone was perforated by crater corrosion after 540 

 days of exposure at the surface. 



Weld beads in Ni-Fe-Cr 800 alloy, made by the 

 TIG process with filler metal 82, were perforated by 

 line corrosion along their edges after 402 days of 

 exposure at the 2,500-foot depth, and both the weld 

 beads and heat-affected zones were attacked by 

 tunnel corrosion after 540 days of exposure at the 

 surface. There was line corrosion along the edge of 

 the weld beads when Ni-Fe-Cr 800 alloy was welded 

 by the manual shielded metal-arc process using 

 electrode 138 after 402 days of exposure at the 

 2,500-foot depth. Both the weld beads and heat- 

 affected zones were perforated by corrosion after 540 

 days of exposure at the surface when Ni-Fe-Cr 800 

 alloy was welded by the manual shielded metal-arc 

 process using electrode 182. 



Weld beads in Ni-Fe-Cr 825 alloy, made by the 

 TIG welding process with filler metal 65, were 

 uncorroded after 402 days of exposure at the 

 2,500-foot depth and after 181 days of exposure at 

 the surface; the weld beads and heat-affected zones 

 were attacked by incipient pitting corrosion after 540 

 days of exposure at the surface. When butt welds 

 were made by the manual shielded metal-arc process 

 using electrode 135, the weld beads were uncorroded 

 after 181 days of exposure at the surface and 189 

 days of exposure in the bottom sediment at the 

 6,000-foot depth; there was incipient pitting of the 

 weld bead after 189 days of exposure in the seawater 

 at the 6,000-foot depth; one end of the weld bead 

 was corroded after 402 days of exposure at the 

 2,500-foot depth; and there was crater corrosion of 

 the heat-affected zone after 540 days of exposure at 

 the surface. When the weld beads were 3-inch- 

 diameter unrelieved circles made by the manual 

 shielded metal-arc process, they were uncorroded 

 after 189 days of exposure in seawater and in the 

 bottom sediment at the 6,000-foot depth. 



Butt welds and 3-inch-diameter, unrelieved circu- 

 lar welds in Ni-Cr-Mo 625 alloy, made by the TIG 

 welding process using filler metal 625, were 

 uncorroded after 189 days of exposure at the 

 6,000-foot depth and after 588 days of exposure at 

 the surface. 



4.3.5. Galvanic Corrosion 



When AISI 4130 steel was fastened to Ni-Cr-Fe 

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

 severely corroded and the Ni-Cr-Fe 600 alloy was 

 uncorroded after 403 days of exposure at the 

 6,000-foot depth [7] . This shows that the 4130 steel 

 was the anodic member of the couple and was being 

 sacrificed to protect the cathodic nickel alloy. When 

 Ni-Be alloy was fastened to Ni-Cr-Fe 600 alloy in a 

 surface area ratio of 1:2, the Ni-Be was severely 

 attacked with there being a much lesser amount of 

 corrosion on the Ni-Cr-Fe 600 alloy. 



4.3.6. Mechanical Properties 



The effects of exposure on the mechanical pro- 

 perties of five of the nickel alloys are given in Table 

 34. The mechanical properties of Ni-Fe-Cr 825 and 

 Ni-Mo-Cr C alloys were not affected. However, there 

 were significant decreases in the elongations of alloys 

 Ni-Cr-Fe 600, Ni-Fe-Cr 902, and Ni-Be, 1/2HT. 



4.4. STRESS CORROSION 



The susceptibility of some of the nickel alloys to 

 stress corrosion is given in Table 35. None of the 

 alloys tested were susceptible to stress corrosion 

 cracking at both the 2,500-foot and 6,000-foot 

 depths for exposures of at least 400 days duration. 



93 



