MIL-DTL-24625A(SH)
3. REQUIREMENTS
3.1 First article. When specified (see 6.2), a sample shall be subject to first article inspection in accordance
with 4.2.
3.2 Recycled, recovered, or environmentally preferable materials. Recycled, recovered, or environmentally
preferable materials should be used to the maximum extent possible, provided that the material meets or exceeds the
operational and maintenance requirements, and promotes economically advantageous life-cycle costs.
3.3 Construction.
3.3.1 Anodes. Anodes shall be constructed of platinized niobium or tantalum (for Class I only), with the
exception of Grade C anodes.
3.3.1.1 Rod anodes. Grade C rod anodes shall be made as follows. The base for application of platinum shall
be a rod (minimum of 0.375 inches in diameter) consisting of a copper core clad with niobium. The ratio of copper
to niobium shall be 60 to 40 by cross-sectional area. The diameter of the anode rod and thickness of platinum
cladding shall be sufficient to achieve the desired anode output characteristic and life (see 3.5.1 and 3.6.1).
3.3.1.2 Wire anodes. The specimen shall register a maximum resistance of 1.69 ohms per 100 feet at
temperature 20±4 °C. If the resistance is greater is greater than 1.69 ohms per 100 feet, the specimen shall be
declared unsatisfactory (see 4.4.6).
3.3.2 Anode holder. Anode holders shall be able to resist dissolution in accordance with 4.4.8. Grade C anodes
shall withstand bending during field application to a radius greater than or equal to 3 inches. Edges shall provide a
suitable and adequate bonding surface for surrounding coating. Holders shall be shock tested as specified in 4.4.7.
3.4 Material.
3.4.1 Platinum plating. The platinum plating shall consist of 99.9 percent pure platinum on an etched surface.
Thickness of the plating shall be determined through calculations of dissolution at 50 percent of maximum current to
last for 20 years, but, in no case, less than 0.002-inch. Verification of the calculations must be provided to the
technical authority.
3.4.1.1 Adhesion. Adhesion of the platinum to the substrate shall be by a metallurgical bonding method (e.g.,
swaging, rolling, welding, explosion bonding). Electroplating of the platinum to the substrate is not allowed, except
as approved by NAVSEA.
3.4.2 Niobium substrate. The substrate shall be 99.9 percent pure, annealed niobium.
3.4.2.1 Rod anodes. Within the base rod, the ratio of copper to niobium shall be 60 to 40 by cross-sectional
area. The copper core shall be commercially pure annealed copper. The anode shall bend as specified in 4.4.3.
Grade C rod anodes shall exhibit no visual cracking of the platinum plating when tested in accordance with 4.4.2 and
4.4.3.
3.4.3 Electrical cable. All electrical cable shall conform to MIL-DTL-915 with type, gauge, and length to be
determined by ship procurement specifications. Cabling shall pass chemical resistance tests found in 4.4.8.
3.4.4 Watertight connection. Following hydrostatic cycling, there shall be no evidence of mechanical damage,
water leakage, or impaired electrical characteristics. Additional requirement for Class 2 anodes are contained in
NAVSEA Technical Manual, NAVSEA S9320-AM-PRO-020. The following electrical characteristics requirements
shall be met following the watertight connection test (see 4.4.5).
3.4.4.1 Electrical resistance. The resistance measured from cable to anode shall be less than 0.01 ohm. This
shall be measured using a meter with a resolution better than 0.1 milliohm.
3.5 Workmanship.
3.5.1 Platinized niobium. The surface of the platinized niobium shall be smooth and free of visible dents,
cracks, kinks, and other defects of a similar nature that may affect serviceability.
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