Post by allan on Apr 2, 2009 13:31:20 GMT
I will be taking Cobby girl out of the water soon and I want sort the anode etc. I contacted McDuff, I have added the emails below and would be interested to hear opinions.
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Thank you for your enquiry. We do get a lot of owners from Cardiff Bay asking about the best anodes to use, and really there is no ideal solution. The correct anode for salt water is Zinc, fresh water is Magnesium and brackish requires Aluminium. However when each type is put into the wrong environment, each has its own problems. Magnesium in salt water is very reactive and will waste very quickly, we recommend that you spend no longer than 7 days in one go or 14 days in any one year. Zinc anodes may passivate when used in fresh water developing a film that will stop the anode from working when you return to salt water. This will need to be scrubbed off with a wire brush to allow the anode to work again. Aluminium is ideal for brackish waters and can also be used in salt water. However in fresh water it does not have enough driving potential to provide adequate cathodic protection.
We often advise the use of hanging anodes. These should have no effect or damage existing hull mounted anodes, however, if the hanging anode corrodes preferentially to the hull mounted anode, the bolts securing it may corrode. Whilst moored in fresh water a Magnesium hanging anode (correctly bonded) should provide adequate protection of the stern gear. Then when the boat sets off into salt water it can be lifted and stowed away. If the boat is going to spend long periods of time (moored) in salt water you could use a Zinc hanging anode, which could then be lifted when the boat is back in fresh water. However this scenario will leave you without protection whilst the boat is underway.
It would also be worth talking to your neighbours who are also moored close to you. Ask them which type of anode they have fitted and if they work well for them.
Just to confuse matters further we have also had reports that Cardiff Bay is not as fresh as previously thought. If the water is found to have a higher salt content then thought, the use of Aluminium anodes may be a good solution. As stated earlier Aluminium can be used in salt water and brackish.
I hope this is of help,
Kind Regards
James Beale
Technical Sales Engineer
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James,
Many thanks for your promt and honest reply. Is it true that things are worse for boats moored in marinas with mains supplies? Our boats are moored on a pontoon but there is no mains power. A few have solar panels and/or wind turbines.
Do you mind if I share your reply?
Regards,
Allan
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Hi Alan,
If you were connected to shore power for long periods of time it is a good idea to have a Galvanic Isolator fitted. If any problems develop from your shore power (which is not uncommon) it will stop steady small currents from small voltages going through to ground; but in the event of a big surge it will allow proper earthing. I don’t mind if you share my reply, in fact any feedback from boat owners moored in Cardiff Bay would be welcome as it will help us understand the situation further.
Kind Regards
James Beale
Technical Sales Engineer
--------------------------------------------------------------------------------
Thank you for your enquiry. We do get a lot of owners from Cardiff Bay asking about the best anodes to use, and really there is no ideal solution. The correct anode for salt water is Zinc, fresh water is Magnesium and brackish requires Aluminium. However when each type is put into the wrong environment, each has its own problems. Magnesium in salt water is very reactive and will waste very quickly, we recommend that you spend no longer than 7 days in one go or 14 days in any one year. Zinc anodes may passivate when used in fresh water developing a film that will stop the anode from working when you return to salt water. This will need to be scrubbed off with a wire brush to allow the anode to work again. Aluminium is ideal for brackish waters and can also be used in salt water. However in fresh water it does not have enough driving potential to provide adequate cathodic protection.
We often advise the use of hanging anodes. These should have no effect or damage existing hull mounted anodes, however, if the hanging anode corrodes preferentially to the hull mounted anode, the bolts securing it may corrode. Whilst moored in fresh water a Magnesium hanging anode (correctly bonded) should provide adequate protection of the stern gear. Then when the boat sets off into salt water it can be lifted and stowed away. If the boat is going to spend long periods of time (moored) in salt water you could use a Zinc hanging anode, which could then be lifted when the boat is back in fresh water. However this scenario will leave you without protection whilst the boat is underway.
It would also be worth talking to your neighbours who are also moored close to you. Ask them which type of anode they have fitted and if they work well for them.
Just to confuse matters further we have also had reports that Cardiff Bay is not as fresh as previously thought. If the water is found to have a higher salt content then thought, the use of Aluminium anodes may be a good solution. As stated earlier Aluminium can be used in salt water and brackish.
I hope this is of help,
Kind Regards
James Beale
Technical Sales Engineer
----------------------------------------------------------------------------------
James,
Many thanks for your promt and honest reply. Is it true that things are worse for boats moored in marinas with mains supplies? Our boats are moored on a pontoon but there is no mains power. A few have solar panels and/or wind turbines.
Do you mind if I share your reply?
Regards,
Allan
----------------------------------------------------------------------------------
Hi Alan,
If you were connected to shore power for long periods of time it is a good idea to have a Galvanic Isolator fitted. If any problems develop from your shore power (which is not uncommon) it will stop steady small currents from small voltages going through to ground; but in the event of a big surge it will allow proper earthing. I don’t mind if you share my reply, in fact any feedback from boat owners moored in Cardiff Bay would be welcome as it will help us understand the situation further.
Kind Regards
James Beale
Technical Sales Engineer