Corrosion / Electrical expert help…..anodes disappearing!

[losangeles10]

I’ve had my Cranchi 33 since new, 20 years ago. 6 months in commission and 6 months hard standing. Anodes always last the time but naturally, replaced every year. Same marina berth for over 10 years. Last year just before lifting out, the Marina stripped out the old bollards and installed new ones with all new wiring and water. This year after 5 weeks in the water anodes 90% gone, shaft on one outdrive failed and a great deal of corrosion. Insurers instructed electrician who could find no fault with the boat, (tested on the hard and also temporarily re floated). The boat has not been connected to shore power. The electrician is not being paid to find any fault in the marina but he did check with his reference cell between the water and earth and got a reading of 425mV and says there is a problem somewhere. He checked the bollard at the end of the line which actually had no earth connection at all! He checked the continuity of the earth between my bollard and the next one along and got a reading of 62,000 ohms. Given I’m not connected to shore power could this nevertheless be the cause of the corrosion? Marina seem to be lacking urgency in looking at this. Given we are talking electricity, salt water and the occasional diver down and we’ve all seen old cables drooping in the water I am surprised to say the least. The boat two doors along has suffered increased anode wear recently but thankfully no corrosion. They hauled out, replaced anodes and went back in. Boat next door says he has always used up anodes quite quickly. He’s attached to shore power but doesn’t know if he has a galvanic isolator and is not very clued up. In any event he’s been the neighbour for 3 years with no issue previously with our boat. I’m not an electrical engineer….is the earth issue a coincidental problem but unconnected? I’m generally not convinced by coincidences…usually means you just haven’t found the reason yet…!

 

[Alex_Blackwood]

I’ve had my Cranchi 33 since new, 20 years ago. 6 months in commission and 6 months hard standing. Anodes always last the time but naturally, replaced every year. Same marina berth for over 10 years. Last year just before lifting out, the Marina stripped out the old bollards and installed new ones with all new wiring and water. This year after 5 weeks in the water anodes 90% gone, shaft on one outdrive failed and a great deal of corrosion. Insurers instructed electrician who could find no fault with the boat, (tested on the hard and also temporarily re floated). The boat has not been connected to shore power. The electrician is not being paid to find any fault in the marina but he did check with his reference cell between the water and earth and got a reading of 425mV and says there is a problem somewhere. He checked the bollard at the end of the line which actually had no earth connection at all! He checked the continuity of the earth between my bollard and the next one along and got a reading of 62,000 ohms. Given I’m not connected to shore power could this nevertheless be the cause of the corrosion? Marina seem to be lacking urgency in looking at this. Given we are talking electricity, salt water and the occasional diver down and we’ve all seen old cables drooping in the water I am surprised to say the least. The boat two doors along has suffered increased anode wear recently but thankfully no corrosion. They hauled out, replaced anodes and went back in. Boat next door says he has always used up anodes quite quickly. He’s attached to shore power but doesn’t know if he has a galvanic isolator and is not very clued up. In any event he’s been the neighbour for 3 years with no issue previously with our boat. I’m not an electrical engineer….is the earth issue a coincidental problem but unconnected? I’m generally not convinced by coincidences…usually means you just haven’t found the reason yet…!

Yes what you say could be the cause of your anode problem. You don't say where you are. Name suggests West coast USA tone of post, UK.
No matter. That marina installation should be shut down and disconnected if your electricians readings are correct. Do not use that supply! The installation is lethal. I do not joke. You have a duty to report the findings to the marina management and their insurance company if you know who they are. The electrician also has a professional duty under H & S legislation(UK) to report it. I would suggest that you should also advise as many other berth holders not to use the shore supply. I reiterate you must report it.

 

[losangeles10]

Yes what you say could be the cause of your anode problem. You don't say where you are. Name suggests West coast USA tone of post, UK.
No matter. That marina installation should be shut down and disconnected if your electricians readings are correct. Do not use that supply! The installation is lethal. I do not joke. You have a duty to report the findings to the marina management and their insurance company if you know who they are. The electrician also has a professional duty under H & S legislation(UK) to report it. I would suggest that you should also advise as many other berth holders not to use the shore supply. I reiterate you must report it.

Thanks Alex, I have told the marina in writing that it could be extremely dangerous. I am amazed the electricians who did the work last year weren’t back working under arc lights to find the problem or at least shut it down and immobilise it from being re-commissioned! Not quite sure what to do if they don’t get it sorted. The marina is in Spain and I am back in the UK and say they are on to it.In the UK I guess it would be HSE or similar. I don’t have a clue how it works out there. I’ve done a lot of reading about corrosion and it seems it is almost always a result of DC rather than AC leak. Rather hoping that someone can explain the science about neighbouring boats being on shore power and my boat suffering extreme corrosion where the earth is extremely poor. Thanks again.