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It’s easy to overlook those small, disappearing pieces of metal attached to your running gear when preparing for spring launch, but that would be a mistake. These sacrificial anodes are the best protection you have against corrosion of your prop(s), rudder(s), trim tabs and other underwater parts — and despite what some people think, they’re not just for saltwater.

Galvanic corrosion occurs when two different metals have physical or electrical contact with each other and are immersed in fresh, salt or brackish water. The resulting electrolytic action can cause pitting, weakening and, ultimately, failure of the more active (less noble) metal part. A sacrificial anode is made to be more active, which means it will divert corrosion to itself and away from your expensive equipment.

The salinity of the water will affect the rate at which an anode deteriorates, and which type of anode material you should use. Zinc and aluminum are most commonly used for salt water, while magnesium is used for fresh water, a much less conductive environment. If you’re going to be boating in both salt and fresh water, aluminum is recommended; it is not recommended to use magnesium anodes in salt or brackish water, as faster corrosion of your metal parts can occur.

Anodes generally require replacement about once a year — spring launch is the perfect time — or when they’ve corroded to about half their original size. In saltwater environments, you may want to replace them every six months. It’s a good idea to check your anode every week.

The need to replace anodes more frequently may indicate a stray electrical current within the boat or at the slip or mooring. You should have this checked by a professional. Alternatively, if anodes don’t need replacing after a year, they may not be providing proper protection. Loose anodes or low grade materials may be the problem. Again, have a pro look things over.

When installing an anode, make sure you have good contact with the metal that’s being protected. Don’t paint between the anode and the metal it contacts, and don’t paint over the anode itself. As always, if you’re unsure of what you’re doing, it’s a good idea to have an expert complete the job. A few extra dollars in labor now could save you in the long run by preventing a costly repair or replacement to one of your underwater metal parts.

United Marine Underwriters is more than just boat insurance. Browse our Used Boats For Sale at Boat Browser or our new Lakes and Waterways’ Guide at Lake Browser. Check out our True Fish Tales – the ones that did not get away – and share your fishing stories.

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2 Responses to Under Armor

  1. Warren says:

    Very informative, thanks!

  2. KEVIN says:

    Very Good Information.

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