corrosion, resulting in many broken wires. The addition of vanadium and 
nitrogen to the basic Type 304 composition did not improve the corrosion 
resistance. The addition of other elements or combinations of elements 
to the basic Type 304 composition did result in increases in corrosion 
resistance of varying degrees, the most improvement being immunity to 
corrosion by the addition of molybdenum, silicon and nitrogen. 
Wire ropes completely immune to corrosion were Ni-Cr-Mo 103, Ni-Cr- 
Mo 625, Ni-Mo-Cr ''C'", Ni-Co-Cr-Mo and Co-Cr-Ni-Fe-Mo. 
Fiberglass monofilament wires became dull and brittle during expo- 
sure. 
CONCLUSIONS 
For a reasonable service life at depth in seawater, three years or 
less, aluminum alloys must be well protected because of their suscepti- 
bility to pitting and crevice corrosion. If protective maintenance can- 
not be performed, aluminum alloys should not be used for deep ocean 
applications. 
Nickel base alloy Ni-Cr-Mo 625, unwelded and welded, can be used 
in seawater applications, unprotected, for many years of maintenance- 
free service where its mechanical and physical properties fulfill other 
requirements. The Ni-Cu alloys would not’ be recommended for use in 
seawater at depths because they pit and are susceptible to crevice 
corrosion in stagnant seawater -- also Ni-Cr-Fe 600 alloy because it is 
susceptible to crevice corrosion. Because of their tendency to pit, 
especially in the welded condition, Ni-Cr-Fe 718 and Ni-Fe-Cr 825 
alloys can be recommended only for limited service in seawater. 
Steels and cast irons, because of their uniform corrosion, can be 
recommended for seawater applications, especially when adequately pro- 
tected. 
A 1 oz/ft? aluminum coating will protect steel for a longer period 
of time than will a 1 oz/ft* zinc coating. 
Stainless steels AISI Type 316 and 20Cb-3 alloy, because of their 
susceptibility to crevice corrosion and pitting corrosion, would not be 
recommended for deep sea applications except under special and unusual 
circumstances. 
Two precipitation hardening stainless steels, 362 and 455, also 
must be protected for short duration deep sea applications. Paint 
coatings containing zinc rich primers and epoxy topcoats provided good 
protection for 6 months. 
Titanium alloys, except for 13V-11Cr-3Al, are recommended for sea- 
water applications in the unprotected condition. 
An 18 percent Ni maraging steel, heat treated to a yield strength 
of 300,000 psi, would not be recommended for seawater applications be- 
cause of its susceptibility to stress corrosion cracking at stresses 
equivalent to 50 percent of its yield strength and above. 
