Question: I'm beginning to put together the spring ownership list for my boat and am wondering about the anodes on my propeller shaft. My boat has ii as shown in the photo, simply I'm wondering if that is really enough to protect my boat for the whole flavor. I proceed the gunkhole in salt h2o and commonly launch just before Memorial Twenty-four hours and booty out right subsequently Columbus Mean solar day in October.

anode-count

The number of anodes needed depends on how much exposed underwater metallic your boat has, and on the time betwixt replacements.

Answer: The number and type of anodes you use on your boat should never exist based on guesswork. First of all, the anode textile is important to ensure adequate protection and service life. Recollect it this way:


  • Saltwater: Zinc or aluminum alloy anodes

  • Stagnant water or for boats that drift between fresh and salt water: Aluminum alloy anodes only

  • Fresh water: Magnesium alloy anodes. Never use magnesium in salt or brackish water!


The reason for the above recommendations is that the relative conductivity of the various waters is different. The protection potential (actually measured in volts) is progressively stronger for the zinc, aluminum and magnesium alloys. Magnesium is the highest and used in the h2o with the to the lowest degree conductivity, fresh water.

As for the number of anodes, it will vary from one boat to another depending upon the corporeality of exposed underwater metal. It is non foolish to presume that if two worked well last year and yous did not require a mid-season replacement, so ii will piece of work for this flavor.

The surface area of anodes exposed to the water is what determines the protection level (in volts). One time you reach the maximum potential for the fabric the anodes are synthetic of, any additional anodes added volition simply add to mass of sacrificial metallic and increment the service interval.

A trained corrosion specialist tin easily determine the right number of anodes for a given boat and once that is done, y'all just demand to repeat and replace the number each season—as long as you don't change the corporeality of exposed underwater metal. One time anodes are physically depleted by about fifty% of their original mass, they should exist replaced.

For a bit more data on this topic, check out my previous post, Protecting Against Marine Corrosion.

Written by: Ed Sherman

Ed Sherman is a regular contributor to boats.com, as well as to Professional Boatbuilder and Cruising World, where he previously was electronics editor. He also is the curriculum director for the American Boat and Yacht Council. Previously, Ed was chairman of the Marine Technology Department at the New England Establish of Technology. Ed's blog posts appear courtesy of his website, EdsBoatTips.