All rudder/trim tab aluminum anodes have stainless steel nuts that are pressed in.  Wear indicator installed

Diameter: 5"(127mm) 

Thickness of (1) Half: 5/8" (16mm)

Weight: 1.82lbs

Do your products meet Mil-Spec?

Yes!  Sacrificial anodes must be impurity-free to properly work, and all our anodes are made only from Mil-Spec alloys. Our zinc anodes are also compliant to ASTM B418 Type 1.  Our Aluminum anodes conform to Mil-Spec A-24779(SH)

How much zinc do I need on my boat?

First, the larger the surface area of an anode, the higher its electrical current capacity and galvanic holding voltage.  For most boats, you want your anode surface area to be sufficient to maintain all underwater metals between -900 mV and -1100 mV relative to a silver/silver-chloride reference electrode.

Second, the longevity of a sacrificial anode is a function of its weight -- the greater the weight the longer its life.

Due to differences in water salinity, temperature, stray currents, and other external influences, you only know the right weight by actual trial.  Periodically inspect your zincs, and when they have corroded to under 50% their original weight they should be replaced.  To lengthen the replacement interval, increase the weight of zincs used.

We've designed hundreds of corrosion protection solutions for metal boats and underwater metal structures such as docks, boat lifts, and retaining walls.