MIL-DTL-18001L Class 2 Type ZRN Rods

Lead-freeMIL-DTL-18001L 0.675" x 72" 0.840" x 72" 1/2" NPT Pencil Anode Stock 10.4 lb Rod

MIL-DTL-18001L Class 2 Type ZRN zinc rods with full mill certification. Three diameters in 72" lengths. Used as pencil anode stock and for marine cathodic protection rod applications.

Solidus

787°F (419°C)

Liquidus

787°F (419°C)

Density

0.258 lbs/in³ (7.13 g/cm³)

Primary Elements

Nominal Composition

99.55% Zn

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Product Overview

MIL-DTL-18001L Class 2 Type ZRN Zinc Anode Rods are full-length zinc rods supplied with complete mill certification to MIL-A-18001L including chemical and physical test documentation. Available in three standard diameters – 0.405″, 0.675″, and 0.840″ – all at 72″ (6 foot) length the rods serve as the primary stock for pencil anode fabrication (cut and threaded for installation in marine engine cooling passages and hull fittings) and as continuous rod anodes for cathodic protection of marine shafting, pipelines, and structural steel. Manufactured by Belmont Metals with full traceability to MIL specification requirements. Class 2 designation indicates the higher alloy quality level of MIL-DTL-18001L confirming the aluminum, cadmium, and trace element composition required for consistent cathodic protection potential in seawater. The 72″ rod length allows custom cutting and threading to any specified pencil anode length from 1″ to 24″. Sold individually by diameter and length.

Available Forms

.675" Diameter x 6' Long, .840" Diameter x 6' Long

Product Code

899Y

Technical Info

Thermal Properties

Melting Point (Solidus)787

Melting Point (Liquidus)787

Physical Properties

Density (imperial)0.258

Density (metric)7.13

Physical Properties

Primary ElementsZn

SpecificationMIL-DTL-18001L

Lead FreeYes

Performance tags

0.675" x 72"0.840" x 72"1/2" NPT Pencil Anode Stock10.4 lb Rod3/4" to 1" NPT Pencil Anode Stock6.75 lb Rod72" Length Custom Cut and ThreadFull Mill CertFull Mill CertificationHigher Mass Per Inch Than 0.675" RodMIL-DTL-18001L CL.2Multiple Anodes Per RodPencil Anode StockThree Diameters 0.405" to 0.840"

Nominal Composition

99.55% Zn

Frequently Asked Questions

Common technical inquiries regarding MIL-DTL-18001L Class 2 Type ZRN Rods

MIL-DTL-18001L Class 1 and Class 2 both specify zinc alloy with aluminum (0.1-0.5%) and cadmium (0.025-0.07%) additions but Class 2 has tighter limits on iron (maximum 0.005% vs 0.014% for Class 1) and lead. Class 2 is the higher-purity designation and is required for ZRN rods and applications where the tighter composition control is needed for consistent electrochemical performance. The full mill certification provided with Class 2 material documents the heat chemistry and mechanical test results for each production lot supporting traceability requirements for government procurement.

ZRN rods are cut to the specified pencil anode length using a bandsaw or lathe parting operation then threaded on one end using a standard pipe die or NC thread die matching the brass plug thread specification. The cut end is faced flat and deburred before threading. Thread engagement length must be sufficient to achieve the MIL-specified pullout strength - typically 1.5 to 2 times the thread diameter. The brass plug is then threaded onto the zinc rod before packaging. This cut-and-thread operation can be performed by distributors, job shops, or end users with standard metalworking equipment.

Pencil anode diameter is matched to the diameter of the threaded hull port or engine block fitting. The 0.405" rod is used for the smallest fitting sizes (3/8" NPT plugs) the 0.675" rod for intermediate sizes (1/2" NPT plugs) and the 0.840" rod for larger fittings (3/4" to 1" NPT plugs). The rod diameter must clear the fitting bore with sufficient annular space for seawater or coolant flow around the anode. The anode length is determined by the depth of the passage being protected and the required zinc mass for the service interval.