VicS
Well-Known Member
Not suggesting that. It wouldn't help anyway if its the steel piling that's causing the problem .... it'll save all their anodes though!
Unplug your own is what I was suggesting.
The Strange Case of Disappearing Anodes and Disintegrating Propellors
- Thread starter Boreades
- Start date
Unplug your own is what I was suggesting.
BrianH
Well-Known Member
When I owned a Trapper 500 and hauled every year to antifoul and renew anodes I once found deep pitting on one side only of the iron keel, which hadn't been there the previous year. It coincided with the arrival of a new neighbour on the side of the pitting (we moor stern-to or bow-to the piers). This newcomer was the original neighbour from hell, noisy, sloppy and with the dirtiest fenders imaginable, that scoured into my topsides until I bought much bigger ones than he had.
I had noticed that this neighbour left his shore power permanently plugged into the supply, which is strictly proscribed in the marina regulations for unoccupied boats, but being in Italy very often not controlled. Some marineros would trip it off (a button flipped the plug round to disconnect) but not remove the plug so that it needed close inspection to ascertain if there was indeed a live connection to the boat.
This seemed a sensible rule as 220 volt appliances permanently switched on can fail and burn - with damage to the immediate neighbours. In fact, just such an occurrence happened on an adjacent pier while I was in the marina last year; the owner had inadvertently left a hot-plate switched on when he left the boat.
But I believe that shore power on adjacent boats can also induce all manner of electrical currents in the water if the wiring is defective, which would exactly fit the diy standard modus operandi of my neighbour. Luckily he moved after only one year and I had no further problems with my keel.
sandyVarne
New Member
Does size of bonding cable matter
7 years ago I replaced all the bonding cables, the advice from Richard Lewis of Salcombe was to use the largest size battery type cable as low current flows easier the larger the cable.
Last year the shaft anode fell off on haul out, and the doughnut MG Duff was hardly touched, this led me to check the continuity from the engine. Going to Waypoint 1 QAB to be advised that a very much smaller (earthing type) bonding cable was fine, they "fitted them all the time with no problems".
This year on haul out the shaft anode was very bad again, the doughnut although a little pitted was not as degraded as each year for the last 7 years. This has led me to believe I was mis-informed by Waypoint. This is just a suspicion. Is it possible every/most boats with trouble have the smaller bonding cable ????? I wonder.......
7 years ago I replaced all the bonding cables, the advice from Richard Lewis of Salcombe was to use the largest size battery type cable as low current flows easier the larger the cable.
Last year the shaft anode fell off on haul out, and the doughnut MG Duff was hardly touched, this led me to check the continuity from the engine. Going to Waypoint 1 QAB to be advised that a very much smaller (earthing type) bonding cable was fine, they "fitted them all the time with no problems".
This year on haul out the shaft anode was very bad again, the doughnut although a little pitted was not as degraded as each year for the last 7 years. This has led me to believe I was mis-informed by Waypoint. This is just a suspicion. Is it possible every/most boats with trouble have the smaller bonding cable ????? I wonder.......
fisherman
Well-Known Member
Maybe no help to you, but we lose anodes very quickly in Newlyn, and it is said this is due to welding activity on steel boats, they should earth the hull to the quay, apparently.
sandyVarne
New Member
Thankyou for your reply.
This might be a reason for high anode degradation in the Saltash, Torpoint, and Mayflower areas. Caused perhaps by a change of welding policy rules by the Dockyard. Would I be correct ?
This might be a reason for high anode degradation in the Saltash, Torpoint, and Mayflower areas. Caused perhaps by a change of welding policy rules by the Dockyard. Would I be correct ?
NorthUp
Well-Known Member
Lots of welding going on here for years, never any problems.
Its unlikely to be welding currents, much more likely to be a shore power problem- if not at a local 240v level, any national grid sized transformers in the vicinity?
Its unlikely to be welding currents, much more likely to be a shore power problem- if not at a local 240v level, any national grid sized transformers in the vicinity?
garvellachs
Well-Known Member
On lift out this year at the end of October our shaft anode and prop anode had completely gone - brand new in April. Last year they were still there but very corroded. That's in the Conwy River on a swinging mooring. The Prowell feathering prop and shaft looked OK.
marcost
Member
anodes and marina's
somethimes there are electrical problems in the marina with earth conductor
it is not totally safe but if for the 220 V shore power, you disconnect the earth conductor, you will not have problems with bad connections on the shore
somethimes there are electrical problems in the marina with earth conductor
it is not totally safe but if for the 220 V shore power, you disconnect the earth conductor, you will not have problems with bad connections on the shore
njthake
Active Member
Anode standards?
The history of the recent short life for anodes, including boats on swinging moorings, coupled with the fact that metal prices went skywords last year makes me suspicious of the alloys currently used in these anodes.
My chandler is very happy to sell me an anode for £70 when the same thing at Beaulieu costs £10.
Is there any standard of what constitutes a Zinc anode? Is it pure or alloyed.
Perhaps recently in order to maintain profit margins (or to increase them) they have been made with a cheaper (or dirty) metal in the alloy?
Nick
The history of the recent short life for anodes, including boats on swinging moorings, coupled with the fact that metal prices went skywords last year makes me suspicious of the alloys currently used in these anodes.
My chandler is very happy to sell me an anode for £70 when the same thing at Beaulieu costs £10.
Is there any standard of what constitutes a Zinc anode? Is it pure or alloyed.
Perhaps recently in order to maintain profit margins (or to increase them) they have been made with a cheaper (or dirty) metal in the alloy?
Nick
dratsea
Well-Known Member
Keith,
I agree with all comments about circuits but there can be a more direct problem with metals in the water. I had my galvanised chain vitually stripped of zinc in 24 hours anchored in a river in Malaysia. Only afterwards worked out that colour of water was the washings from the local tin mine. I remember something in chemistry at school along lines of tin on steel (for "tin cans") because the tin would migrate into any internal scratches without poisoning future end user. If tin or whatever other metal/acid/solvent will take the zinc off a chain then can tin displace zinc from an anode and ultimately the prop? Has the increase in acidity leached the tin (metal/acid/solvent) out of the old mine workings? Little sister did her MSc at University of Plymouth Marine Biology Unit on effects of old mine workings on ecology of local rivers. Should see her over Christmas and will try to find out more.
John
I agree with all comments about circuits but there can be a more direct problem with metals in the water. I had my galvanised chain vitually stripped of zinc in 24 hours anchored in a river in Malaysia. Only afterwards worked out that colour of water was the washings from the local tin mine. I remember something in chemistry at school along lines of tin on steel (for "tin cans") because the tin would migrate into any internal scratches without poisoning future end user. If tin or whatever other metal/acid/solvent will take the zinc off a chain then can tin displace zinc from an anode and ultimately the prop? Has the increase in acidity leached the tin (metal/acid/solvent) out of the old mine workings? Little sister did her MSc at University of Plymouth Marine Biology Unit on effects of old mine workings on ecology of local rivers. Should see her over Christmas and will try to find out more.
John
Bosun Higgs
N/A
Your experience begs the question of whether the chain was properly hot dipped to the appropriate BS or just spun galved with the lightest possible coating - as most of our stuff is these days. galvanised shackles from the usual 3rd world suppliers seem to last a matter of a couple of weeks immersion before rust appears. The few bits I have left and which I had galvanised in our hot dip bath last years by comparison.
To the OP. Most of the answers above speculate about marina piles etc but I dont see how that can answer the problem of boats out on moorings. If indeed the problem is something in the water then there are few alternatives - protest to the environment agency about water quality, move moorings, make the boat inert.
The environment agency have very wide powers if you can fire them up and you might well do that with a concerted campaign. I used to have enhdless problems with them about zinc leaching from old workings on our site and ended up having to install some very expensive kit to minimise it even though it wasnt the result of anything we had done. The liability is a strict one on the property owner.
You could make the boat reasonably inert with marelon seacocks and a kiwi type prop. Big anodes on wires dropped over the side at the pontoon.
To the OP. Most of the answers above speculate about marina piles etc but I dont see how that can answer the problem of boats out on moorings. If indeed the problem is something in the water then there are few alternatives - protest to the environment agency about water quality, move moorings, make the boat inert.
The environment agency have very wide powers if you can fire them up and you might well do that with a concerted campaign. I used to have enhdless problems with them about zinc leaching from old workings on our site and ended up having to install some very expensive kit to minimise it even though it wasnt the result of anything we had done. The liability is a strict one on the property owner.
You could make the boat reasonably inert with marelon seacocks and a kiwi type prop. Big anodes on wires dropped over the side at the pontoon.
pappaecho
Well-Known Member
Luckily we do not seem to have the same problem in Pompey harbour. However, I have recently unearthed ( no pun intended) some Old anodes, which were bought at a boat jumble ten years ago and got mislaid. Would be more than happy to donate one of them for chemical analysis and comparison with anodes on sale in the last couple of years to see if there is a change in the chemical constituents, given that in the last few year the prices of zinc, aluminium and magnesium have rocketed. It could be that the change in the metals ratio have have resulted in increased depletion with other factors which seem to affect some harbours and not others. PM me if you want a sample of a new anode nominally 10 years old and new.
Bobobolinsky
Well-Known Member
Having a couple of galvanisers as club members (ZLYC) is quite helpful as we suffer horrendous corrosion rates in the Mzingazi Canal. A couple of the members got hold of galvanising zinc to melt for anodes. Result anodes that didn't work. Still trying to figure out if galvanising zinc is not what it's sold as
Chris_Robb
Well-Known Member
First of all, the shaft anode is doing its job, and loosing metal protecting the shaft. I would therefore not expect the large anode to really do much, therefore will not loose much - what else is their to protect?
Second, why install fat cables? They are at best carrying only a very small currenst so thin will do just as well as fat. Fat holds no benefit until the amps are much higher, which I hope you will not ever see with your anodes!!!!
Your situation sounds perfectly normal.
Seanick
Well-Known Member
Agree with VicS,
Unplug your shore power.
Disconnect the galv isolator when not in use, or fit a switch.
Leave your batteries turned off.
Check for continuity across the shaft coupling.
Don't bond skin fittings to the anodes.
Monitor for improvements or otherwise!
Unplug your shore power.
Disconnect the galv isolator when not in use, or fit a switch.
Leave your batteries turned off.
Check for continuity across the shaft coupling.
Don't bond skin fittings to the anodes.
Monitor for improvements or otherwise!
rudolph_hart
Well-Known Member
Keith, we're on a swinging mooring, and I replace anodes each year. I have noticed a distinct increase in anode erosion recently.
4 years ago a small shaft anode would be half eaten after a season.
3 years ago a single anode was gone, so next season I fitted two.
2 years ago one was gone and the 2nd a quarter eaten.
Last year BOTH had gone in a season, so I splashed out on a BIG Duff shaft anode (bullet-shaped) for this season.
This year On haulout it's gone!
I am a bit concerned, because I've got a Volvo 3-blade folding prop - v. expensive to replace.
Last edited:
Quester
Member
Don't bond skin fittings?
Seanick says "Don't bond skin fittings". Was this a typo?
I thought the right thing to do was to bond everything including skin fittings (sea cocks), engine, electrical system earth, saildrive etc. back to the main anode. This is the approach that I have taken. The main anode is not suffering much but I have noted a build up of a powdery deposit on the capture bolts (bronze) of my Blakes sea cocks on the inside of the hull. What is this? Is this a result of the bonding - I certainly wasn't aware of it before bonding. Have I made a mistake in bonding the skin fittings?
Seanick says "Don't bond skin fittings". Was this a typo?
I thought the right thing to do was to bond everything including skin fittings (sea cocks), engine, electrical system earth, saildrive etc. back to the main anode. This is the approach that I have taken. The main anode is not suffering much but I have noted a build up of a powdery deposit on the capture bolts (bronze) of my Blakes sea cocks on the inside of the hull. What is this? Is this a result of the bonding - I certainly wasn't aware of it before bonding. Have I made a mistake in bonding the skin fittings?
dukes4monny
Well-Known Member
My understanding is that it's best not to bond your skin fittings / seacocks as they then become part of the circuit instead of being isolated.
It shouldn't be a problem if your anodes are in order, but if they get completely eroded then I would be worried.
I would suggest that you check with a competent marine electrician to confirm this though.......
Conrad
Well-Known Member
Not a good idea, in the UK the earth is there for protection purposes, the protection being if you have a fault items likes taps, metal cases of kettles and so on don't remain live and zap you because the circuit goes to earth generating a fault current that blows the fuse.
A positively shocking suggestion don't do it.
Regards
Conrad
boatmike
Well-Known Member
A very interesting story. I can't provide a solution but before I retired I was a project manager at a local shipyard in Southampton on the Itchen river. As the yard is now moved to Portsmouth I don't have any professional conflict in telling this. Local readers will know the company so I will say that none of this is a criticism of the yard or the company and does not breach confidentiality. The river moorings alongside were used to fit out vessels after launch. Many large warships were so treated on the lower part of the moorings and to my knowledge never had electrolysis problems, perhaps because of the very careful anodic protection afforded them. On the upper part however where I was unfortunate to have to moor several smaller commercial vessels the electrolytic corrosion was very rapid and extreme. One difference was that being smaller vessels, they were close in to old steel piles. We tried mooring to a double width floating pontoon to get them further out and that helped. We used very large "over the side" anodes and that helped too but the problem was never entirely solved and no analysis or "expert" assistance really made a difference or identified the source of the problem. One theory was that because these moorings were relatively shallow and the steel piles many and massive, it was simply a matter of proportion. Certainly nothing to do with acidity as the tidal flow was considerable and the same for the other moorings downstream anyway. We tried stopping all welding on board or nearby....no difference. We once had a very clever chap with a box of electronic gubbins checking the PD between piles and vessel, different parts of vessels and the river bed and the vessels. The most interesting result was that the problem was at it's maximum at lowwater spring tides when there was a discernable flow between the bottom and the boat. We never found out if this was due to old metal structures below the bottom or even something sunk there in the past. Who knows? Geophysical analysis showed nothing..... It all only helps to add to the mystery I know but I am sure these things are often very difficult to pin down or attribute to a single cause.....
