What's a "normal" length of time between zinc replacements, assuming there are no unusual sources of electrolysis (is that the right word?). Can your own boat be the source if it is sitting at the dock with all power turned off? I have a diver clean the bottom of my boat monthly and he replaces the zinc every two to three months. I'm wondering if the boat bottom is the only thing being "cleaned".
Zinc replacement
- Thread starter AllenF
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Various factors conspire to erode the zincs, notably electrolysis (whatever that is). I'm off the Chesapeake Bay, and our diver replaces the zinc once or twice a year. So yes, the bottom is the only thing being cleaned.
You may want to have your diver supply you with the old zincs for inspection. If the zinc is more than half consumed, the replacement is legit.
I would think that four or five replacements/year is excessive. Either you have electrolysis in your spot or your wallet is also being cleaned (out). You may also want to install extra zincs to increase the replacement period if you do indeed have a problem.
I would think that four or five replacements/year is excessive. Either you have electrolysis in your spot or your wallet is also being cleaned (out). You may also want to install extra zincs to increase the replacement period if you do indeed have a problem.
Depends where you are.
If in a slip... could be some weird stuff with the AC current... or you could have an in-house leak. Your boat may not be the source... however you could be the recipient.
I am on a mooring for for 5 months out of the year. Every-time my boat gets hauled in the fall... there IS NO ZINC left.
Have the diver give you the zinc he replaced... if there is one.
If in a slip... could be some weird stuff with the AC current... or you could have an in-house leak. Your boat may not be the source... however you could be the recipient.
I am on a mooring for for 5 months out of the year. Every-time my boat gets hauled in the fall... there IS NO ZINC left.
Have the diver give you the zinc he replaced... if there is one.
My zinc looks almost new after a full season, it doesn't look like it's lost any material, it's just not shiny. I'm not sure if it has anything to do with it but i'm in freshwater and I never leave the shore power connected unless I'm there. I also turn the battery switch to off if I'm not there.
Manny
Manny
Fresh Water is Different
Manny,
You should not be using zinc as the sacrificial anode in freshwater. I think the correct metal is magnesium or even aluminum, but check at the supplier for the product they recommend.
Patrick, I would be suspicious if my zincs lasted 2 years and still looked new. To me, this is very unusual. The zinc is designed to be the sacrificial "lamb" to protect the other metals below your waterline. Even with a galvanic isolator (I have one on my boat too) you should still see some eroding of the zinc. Even if your boat is well "isolated" from the shore power, there are other sources of corrosion. If you put two different metals into a solution (salt water) you create a type of battery. One metal will erode or sacrifice itself under these conditions. The metal that will erode is the "least noble of the two". There is a scale listing the various metals in "nobility" order.
Anyway, I am not an expert in this area, but both of these situations should be investigated to ensure that nothing "unusual" is going on unknown to you.
Allen, I agree with the others. Ask to see the replaced zinc. They can't always be completely consumed.
Good luck,
Tom
Manny,
You should not be using zinc as the sacrificial anode in freshwater. I think the correct metal is magnesium or even aluminum, but check at the supplier for the product they recommend.
Patrick, I would be suspicious if my zincs lasted 2 years and still looked new. To me, this is very unusual. The zinc is designed to be the sacrificial "lamb" to protect the other metals below your waterline. Even with a galvanic isolator (I have one on my boat too) you should still see some eroding of the zinc. Even if your boat is well "isolated" from the shore power, there are other sources of corrosion. If you put two different metals into a solution (salt water) you create a type of battery. One metal will erode or sacrifice itself under these conditions. The metal that will erode is the "least noble of the two". There is a scale listing the various metals in "nobility" order.
Anyway, I am not an expert in this area, but both of these situations should be investigated to ensure that nothing "unusual" is going on unknown to you.
Allen, I agree with the others. Ask to see the replaced zinc. They can't always be completely consumed.
Good luck,
Tom
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Re: Fresh Water is Different
Proper term is galvanic corrosion . And the post give great info on replacing the zincs . Don't forget the pencil zincs found in the heat exchange ,and in some engine blocks .
Proper term is galvanic corrosion . And the post give great info on replacing the zincs . Don't forget the pencil zincs found in the heat exchange ,and in some engine blocks .
Thanks for the heads up Tom
Manny
Frankly I didn't realize that there were different types of sacrificial anodes available. I would just go and ask for one at my local chandlery and put it on the prop shaft. As far as my outboard, I'm not even sure if Honda makes different types of anodes for it.
Manny
Yes, the anodes are available in different alloys, depending on the salinity of the water. Magnesium is generally used for fresh water, aluminum for brackish water and zinc for salt water. Using the wrong alloy will result in either insufficient protection, due to the metal not being reactive enough—like using zinc in freshwater; or the anode being eaten away prematurely, leaving you completely unprotected—like using magnesium anodes in salt water.
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