46 CFR 56.60-20 - Nonferrous materials.
Nonferrous materials listed in this subpart may be used in piping systems under the following conditions (see also § 56.10-5(c)):
(a) The low melting points of many nonferrous metals and alloys, such as aluminum and aluminum alloys, must be recognized. These types of heat sensitive materials must not be used to conduct flammable, combustible, or dangerous fluids, or for vital systems unless approved by the Marine Safety Center.
For definitions of flammable or combustible fluids, see §§ 30.10-15 and 30.10-22 or parts 151-154 of this chapter. Dangerous fluids are those covered by regulations in part 98 of this chapter.
(b) The possibility of galvanic corrosion due to the relative solution potentials of copper and aluminum and their alloys should be considered when used in conjunction with each other or with steel or with other metals and their alloys when an electrolyte is present.
(c) A suitable thread compound must be used in making up threaded joints in aluminum pipe to prevent seizing which might cause leakage and perhaps prevent disassembly. Pipe in the annealed temper should not be threaded.
(d) The corrosion resistance of copper bearing aluminum alloys in a marine atmosphere is poor and alloys with copper contents exceeding 0.6 percent should not be used. Refer to Table 56.60-2(a) of this part for further guidance.