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5 Things You Need to Know About Boat Zincs

As most boaters know, underwater electrical current is a threat to immersed metals on your boat. Without proper protection, galvanic corrosion can result in expensive repairs to running gear or even sinking. Protection comes from proper installation and maintenance of sacrificial anodes, commonly known as zincs.

Here are 5 things to know about zincs:

  1. Zinc is not the only metal used for sacrificial anodes. Aluminum anodes tend to last longer on boats operating occasionally or regularly in fresh or brackish water. Magnesium is a good choice for fresh water only operations.
  2. Zincs should be replaced when about half of the anode has been lost to corrosion. The longevity of a sacrificial zinc anode is a function of its weight. When a zinc lasts less than a year, you need one with more weight.
  3. Check zincs every 6-12 months with a dive or haul out. With a new boat or new mooring location it’s especially important to monitor zincs closely until you’re confident they will last a year.
  4. Zincs must be installed so that they physically contact the metal they are protecting. Never coat anodes with paint.
  5. Beyond the hull, many vessels have zincs in the engine cooling water jacket, heat exchangers, stern drive or outboard engine. The owner’s manual or a boat mechanic can help you confirm all of the anode locations on your boat. These should be changed every 6-12 months.