Zinc vs. Aluminum Anodes

Mil-Spec Zinc and Mil-Spec Aluminum anodes provide excellent corrosion protection for steel and aluminum hull vessels that operate in salt or brackish water.  Both are very effective.  Historically, zinc anodes have been less expensive than aluminum but since 2005 that's no longer the case.  The more active, longer lasting aluminum anodes are now less expensive, making them a clear favorite for most commercial applications.

Mil-Spec A-18001K Zinc Anode Mil-Spec A-24779 (SH) Aluminum Alloy

The difference between zinc and aluminum anodes is summarized below:

  Zinc
MIL-A-18001K
Aluminum
Mil-A-24779 (SH)
Voltage (1) -1040 mV -1100 mV
Density 0.258 lbs per cubic-inch 0.105 lbs per cubic-inch
Energy Capacity 368 amp-hours per lb 1150 amp-hours per lb
Service Life (relative to Zinc) 100% 120%
Cost (relative to Zinc) 100% 75%

(1)
 Galvanic voltage produced relative to a silver/silver-chloride electrode in seawater.