Now that you know the basics of why anodes are important for your boat, theoretically how they work, and which metal alloy you should use in your boating environment, let’s talk about how to make sure your anodes are working. After all, you paid for those pieces of metal, so you want to get the most for your money.

ACTIVE vs INACTIVE – An ACTIVE anode is one that is currently in the process of corroding (or as we like to think of it, protecting the important metals on your boat). An INACTIVE anode is one that is no longer or never was corroding, or is corroding at a rate that is not protecting your boat. How can you tell? Great question!

WHAT DOES ACTIVE LOOK LIKE? – An active anode may look like it is bubbling, you may see material sluffing from it, or it will be wearing away and getting smaller over time. The bubbling may be very difficult to see, (especially if you’re not in the water) but when it happens it looks like a subtle version of the reaction between an open wound and hydrogen peroxide. This bubbling will usually be most evident when an anode is first put in the water and has become newly active.

If you get in the water to look under your boat (don’t laugh, some people do it), or you’re able to touch an anode on your boat while it is in the water, you should see a small amount of material (like a puff of dust) sluff off. This shows you that the anode is still active and there is no barrier impeding the flow of ions to the cathodic metal.

WHAT CAN I DO TO MAKE SURE MY ANODES ARE ACTIVE? – First and foremost, you should ensure that the anode has metal to metal contact with the cathode whenever possible. As we discussed before, you are creating a circuit of protection when you use an anodic metal to protect a cathodic metal. This circuit is most effective when the 2 metals are in direct contact with each other. If they are not touching, other cathodic metals nearby may pull from the anode causing it to be less effective.

Anodes can also become inactive if they are exposed to air or a different type of water environment. As discussed in week #5, an anode that is taken out of the electrolyte solution it became active in will form a crust of oxidation causing a barrier that impedes the flow of ions even if you put it back into the same electrolyte solution.

You will never see marine growth on an active anode. If you see any type of sea life attaching itself to an anode, you know that the anode as a whole, or the part where growth is occurring is no longer active. If part of the anode isn’t working properly, then the whole circuit is less effective at protecting your boat. (We’ll talk more about how to avoid this problem in a few weeks). Most importantly, you should not see corrosion on the metal parts of your boat, if you do, it’s very possible that your anodes are not active.

Come back next week to read about specific circumstances that cause anodes to become inactive or less effective and how to avoid those situations.


We understand that it is nearly impossible to check your anodes unless you get in the water and swim under your boat. If you’re in a region or boating environment that allows you to keep your boat in the water for more than a week or two at a time, be sure you have a good diving service.

Along with cleaning marine growth from your boat, you want your diving service to be knowledgeable in proper anode installment and trained in knowing when an anode is no longer active or useful. Your diving service can often show you photos if you ask in advance and should always keep you informed about the “life” of your boat’s anodes. Don’t be afraid to ask your diver questions about your anodes and the bottom of your boat!

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