Electrolysis - How far?

hard1 · 07 December 2005, 23:02

I have a non RIB technical question regarding electrolysis. We have all heard of wrongly electrically connected boats in marinas causing serious damage to surrounding shafts etc through acting as sacrificial anodes, but has anyone on the forum any idea as to roughly the maximum distance other boats can be affected? Or is it purely to do with the amount of current discharging into the water. I have known of boats affected within a 20-30' radius for example, but is this the maximum?

Your assistance would be appreciated.

hard1 · 08 December 2005, 10:23

ttt

codprawn · 08 December 2005, 11:39

A lot would depend on the type of water it is in - ie it's salinity and also how still the water is - massive difference between a small closed marina and a big one with loads of water movement.

hard1 · 08 December 2005, 12:03

[QUOTE=codprawn] A lot would depend on the type of water it is in - ie it's salinity and also how still the water is - massive difference between a small closed marina and a big one with loads of water movement. [/QUOTE

Salinity - Salty, Marina - British. Water Movement - Average. Pontoon Space - Average. Harbourmaster - Grumpy. Grey Mullet - Abundant. Electrical Supply - Shocking. Anodes - Fkd.

fred bolton · 08 December 2005, 12:13

Quote:

Originally Posted by hard1

I have a non RIB technical question regarding electrolysis. We have all heard of wrongly electrically connected boats in marinas causing serious damage to surrounding shafts etc through acting as sacrificial anodes, but has anyone on the forum any idea as to roughly the maximum distance other boats can be affected? Or is it purely to do with the amount of current discharging into the water. I have known of boats affected within a 20-30' radius for example, but is this the maximum?

Your assistance would be appreciated.

My wife has electrolysis treatment, £15 a go, can I attach her to the hull and obtain the same results?

Jono · 08 December 2005, 12:18

Quote:

Originally Posted by fred bolton

My wife has electrolysis treatment, £15 a go, can I attach her to the hull and obtain the same results?

Is that the same as the Electrotherapy I have to undergo as condition of my "Care in the Community" status?..... perhaps I could tell 'em I'm going to live on a boat?...

All this electrickery makes my hair stand on end..and I can't do a thing with it.....

hard1 · 08 December 2005, 12:28

Thank you for your replies. I thought there might be someone on this forum who knows something about marine electrolysis - a friend has suffered serious damage to shafts and P brackets and suspects the presence of a dumb lighter in the marina, which has electrical power to welding sets and zero anodes as the likely cause, but has been faced with denials by marina officials and the barge owners. He is looking at repair bills in the order of £'000's even though his boat is correctly protected as verified by a marine surveyor. I hasten to add that this is not local to me (we have several dredgers and barges in local marinas as I speak).

This seems to be a growing problem in the UK. I just wondered if there was any similar experiences out there, as an aluminum outboard/outdrive leg on a RIB would be eaten in double quick time given the same circumstances, and how would one check, verify and protect against such likelyhoods.

Jono · 08 December 2005, 12:43

Try talking to a good surveyer. The efficiency of your cathodic protection can be measured and checked. I believe that Aluminium can be "over protected" which can also cause big problems. I don't in anyway claim to have any knowledge of the "mechanics" of it all, but it's worth searching for the information. I looked because I was half interested in building metal boats at one time.....

Jono · 08 December 2005, 12:50

Here's a Yank paper on it. It's talking about AC marina systems but you'll notice that they talk about being connected to "every boat in the marina" not physical distance....

Are the welding sets powered off the Marina electrics or are they welding generators?

http://www.boatus.com/seaworthy/galvanic/default.asp

hard1 · 08 December 2005, 13:03

Quote:

Originally Posted by Jono

Here's a Yank paper on it. It's talking about AC marina systems but you'll notice that they talk about being connected to "every boat in the marina" not physical distance....

Are the welding sets powered off the Marina electrics or are they welding generators?

http://www.boatus.com/seaworthy/galvanic/default.asp

Fantastic site. Thanks and it explains a lot, I'll forward it on to my mate. The welding sets are powered from the Marina electrics, and it looks as if he may have an insurance claim, either his or theirs if the survey report on his install holds up. It is also worth noting (for the benefit of members who keep their boats in marinas) that often, the berthing contract small print carries and indemnity against these events but I'm sure there's a "duty of care" issue which may override it.

codprawn · 08 December 2005, 13:10

Quote:

Originally Posted by hard1

Thank you for your replies. I thought there might be someone on this forum who knows something about marine electrolysis - a friend has suffered serious damage to shafts and P brackets and suspects the presence of a dumb lighter in the marina, which has electrical power to welding sets and zero anodes as the likely cause, but has been faced with denials by marina officials and the barge owners. He is looking at repair bills in the order of £'000's even though his boat is correctly protected as verified by a marine surveyor. I hasten to add that this is not local to me (we have several dredgers and barges in local marinas as I speak).

The comments I made were perfectly valid and make a HUGE difference!!!

hard1 · 08 December 2005, 14:50

Quote:

Originally Posted by codprawn

The comments I made were perfectly valid and make a HUGE difference!!!

Valid - probably, HUGE difference - possibly, useful information - no. Thank you anyway.

codprawn · 08 December 2005, 15:04

But thats the whole point - there are so many variables to take into account. It is a simple basic concept that is affected massively by all the variables.

With so many variables to take into account the marina people and the barge owners can wriggle out of almost anything.

hard1 · 08 December 2005, 15:45

Quote:

Originally Posted by codprawn

But thats the whole point - there are so many variables to take into account. It is a simple basic concept that is affected massively by all the variables.

With so many variables to take into account the marina people and the barge owners can wriggle out of almost anything.

Look, I thank you for your input but I didn't want speculation, I wanted tacit assistance. This I got from Jono. Another time I would be only too happy to enter into a debate about the esoterics and theory of marina design, water flow and how these variables could affect electrolysis and galvanitic activity depending on the salinity etc etc.

Thanks once again...

The Garfish · 08 December 2005, 19:46

Quote:

Originally Posted by hard1

Look, I thank you for your input ..........

Thanks once again...

i fink dat ard wan iz bustin a gutt tryin too bee polyte. wot hee reely meens iz shutt de fukk upp

gArf

Hugh Jardon · 08 December 2005, 20:22

Quote:

Originally Posted by The Garfish

i fink dat ard wan iz bustin a gutt tryin too bee polyte. wot hee reely meens iz shutt de fukk upp

gArf

love it and if you know mr ard wan he was being very very restrained and polite indeed, looks like fish boy has got the message anyway!!! makes a fckin change i must say!!

hard1 · 08 December 2005, 21:41

Quote:

Originally Posted by The Garfish

i fink dat ard wan iz bustin a gutt tryin too bee polyte. wot hee reely meens iz shutt de fukk upp

gArf

Hmmmm, I been sussed.

Mollers · 09 December 2005, 07:33

In my opinion, for what it's worth

is that the prob was with your mates boat. I managed a 70ft steel ketch for a guy for a while. Electolisis was a major issue on a boat of this type with numerous AC and DC systems on board. We had marine electrical engineers aboard here and abroad and it is quite a complicated topic. I think, despite what you've been told by a "marine" engineer ( a lot of marine engineers are pretty foggy on this subject) that you had an earth leak. The boat was presumably hooked up to shore power which is the major culprit. The anodes would have soon gone, then the trouble begins. We kept the ketch for months in marinas in Hong Kong. Crete, Malta, Majorca and Lisbon. None of these places are too fussy about pontoon isolation etc and we never had a problem. On the main control panel we had "Earth Leak" warning lights which would glow if we were leaking through the hull or a fitting. If it were from welding or the pontoons why did it not "eat" every boat in the marina? Sorry, but I think that it's dig deep and learn for next time.

In m opinion.

Erin · 09 December 2005, 19:42

Mollulnan's on the right thread I think with his reference to an earth indicator light. Most top spec shore power circuits on a boat will have a 'galvanic isolator'. This isolates the boats earth circuit (which should be bonded to all metal components) from the shore power earth. It allows large currents through in the event of a fault, but stops the small millivolt currents which cause galvanic corrosion. This doesn't mean that there wasn;t something seriously wrong with the marina that caused the problem. Sounds like your mates boat was electroplating the marina pontoons!

Keith

codprawn · 09 December 2005, 20:30

Quote:

Originally Posted by Hugh Jardon

love it and if you know mr ard wan he was being very very restrained and polite indeed, looks like fish boy has got the message anyway!!! makes a fckin change i must say!!

What message??? Please explain it to me oh Hugh one......