Active Galvanic current at work.

[GregOddity]

ACTIVE GALVANIC CURRENT ? ELECTROLYSE?





Let me star by saying that I am not an expert of any kind on galvanic current. It’s a bit of a Dark Art for me I’m afraid.

These are from an LM 27 that I just finished rebuilding the Rudder and Skeg. The boat lost its rudder on the water leaving the marina. It literally dropped off as the skeg disintegrated.

Upon lifting the boat, the skeletal remains of the skeg (which was supposed to be a flat bar mild steel 50x10) where as shiny as if the thing had come out of an acid bath and not the ocean. No growth of any kind on any of the metal surfaces on this boat

The anodes were gone and I mean gone.

Within 30minutes of coming out of the water, the skeg remains had started to oxidate finally turning brown. All through hull skin fittings were badly affected and extremely brittle.

The cutlass bearing housing plus the shaft pipe and all skin fittings were replaced. I fabricated a new skeg and rudder out of Stainless 316 and installed two anodes on the inner top of the rudder and one on the skeg. The cutlass bearing housing is connected by wiring to a bolt on the skeg which also has an anode installed.

All surfaces should be RED from the antifoul.

Boat was splashed Friday last week; first pic is from 2 days later.

I’m merely showing the effects and active galvanic current at work. At this stage I cannot even hazard a guess as to the cause. There’s a 60” Mild Steel boat at the marina not far from this LM. There are also some wiring issues the owner is trying to solve. I’ll update with findings.

 

[Alex_Blackwood]

ACTIVE GALVANIC CURRENT





Let me star by saying that I am not an expert of any kind on galvanic current. It’s a bit of a Dark Art for me I’m afraid.

These are from an LM 27 that I just finished rebuilding the Rudder and Skeg. The boat lost its rudder on the water leaving the marina. It literally dropped off as the skeg disintegrated.

Upon lifting the boat, the skeletal remains of the skeg (which was supposed to be a flat bar mild steel 50x10) where as shiny as if the thing had come out of an acid bath and not the ocean. No growth of any kind on any of the metal surfaces on this boat

The anodes were gone and I mean gone.

Within 30minutes of coming out of the water, the skeg remains had started to oxidate finally turning brown. All through hull skin fittings were badly affected and extremely brittle.

The cutlass bearing housing plus the shaft pipe and all skin fittings were replaced. I fabricated a new skeg and rudder out of Stainless 316 and installed two anodes on the inner top of the rudder and one on the skeg. The cutlass bearing housing is connected by wiring to a bolt on the skeg which also has an anode installed.

All surfaces should be RED from the antifoul.

Boat was splashed Friday last week; first pic is from 2 days later.

I’m merely showing the effects and active galvanic current at work. At this stage I cannot even hazard a guess as to the cause. There’s a 60” Mild Steel boat at the marina not far from this LM. There are also some wiring issues the owner is trying to solve. I’ll update with findings.

If there are wiring issues, it could be "Electrolytic" not Galvanic! The two should not be confused. It is an interesting subject!

 

[GregOddity]

If there are wiring issues, it could be "Electrolytic" not Galvanic! The two should not be confused. It is an interesting subject!

Absolutely, it looks like the anodes are electroplating all the surfaces with tin. It should all be red. Antifoul is 2 days old and red. There’s a bit too much going on in there for me to hazard a guess

 

[VicS]

Absolutely, it looks like the anodes are electroplating all the surfaces with tin. It should all be red. Antifoul is 2 days old and red. There’s a bit too much going on in there for me to hazard a guess

This is not "galvanic" corrosion That is caused by current flowing between two " dissimilar" metals metal driven by a small difference in their electrode potentials

This, I am sure, is electrolysis, caused by current flow driven by an electrical fault on board.

I dont know what you think you mean by "the anodes are electroplating all the surfaces with tin." That's nonsense. ( where's the tin coming from for a start?)

Start looking for a fault that could be a leakage path from your battery positive to the parts most affected. ( rudder and what you are calling the skeg)

When afloat completely disconnect your batteries except while investigating the causes

I'd remove that connection between the skeg and the cutlass bearing and also any electrical connections to skin fittings etc.

(Disconnect your shore power connection to eliminate the effects of a fault on another nearby vessel when afloat)

It will be interesting to hear what other Chemists make of this.

 

[PaulRainbow]

It would be a very good idea to disconnect the trough hulls from the anode bonding circuit, there is no point having them connected and these pictures clearly show the downside to doing so. If the cutlass housing is not connected to anything else metal, it too can be disconnected.

EDIT: typed while VicS posted, i'd echo his comments too.

 

[doug748]

Has someone connected the hull anode to a battery (or otherwise shorted it as suggested above) ? Chap on here did that once and trashed a brand new engine plus running gear.

Disconnect all batteries and see what occurs. (Edit, yes.....as post 4)

.

 

[Tranona]

As others have said this is all wrong. There is no need for anodes where you have them - in fact you have created a problem by connecting the stainless skeg to the bronze cutless housing. Remove that and the anodes - they won't do anything as there are no mixed metals on your stainless rudder or the skeg.

Note you have a hull anode. What is this connected to? It should only be to the prop shaft to protect the prop on the stainless shaft. Remove any connections to the stern tube and through hulls. They do not need connecting to anodes.

Aware repeating advice, but just reinforcing the points. Exactly the same will happen again if you do not disconnect the bonding circuits because it is that which is the source of the problems.

 

[GregOddity]

This is not "galvanic" corrosion That is caused by current flowing between two " dissimilar" metals metal driven by a small difference in their electrode potentials

This, I am sure, is electrolysis, caused by current flow driven by an electrical fault on board.

I dont know what you think you mean by "the anodes are electroplating all the surfaces with tin." That's nonsense. ( where's the tin coming from for a start?)

Start looking for a fault that could be a leakage path from your battery positive to the parts most affected. ( rudder and what you are calling the skeg)

When afloat completely disconnect your batteries except while investigating the causes

I'd remove that connection between the skeg and the cutlass bearing and also any electrical connections to skin fittings etc.

(Disconnect your shore power connection to eliminate the effects of a fault on another nearby vessel when afloat)

It will be interesting to hear what other Chemists make of this.

I have no dog on this race. I merely posted because I thought it would be interesting to hear about the subject from people that have more knowledge about these currents and problems then I do. Also because it’s such an extreme example of these types of problems.

It does look like the anodes are “electroplating” the surfaces around but it’s easy to see that I clearly mentioned anodes when I referenced “tin”. Obviously, I had not yet had my morning coffee and meant Zinc. But I blame it on old age and arthritis on the left pinkie.

The owner is working trough a range of options and I think it will end with hiring someone to solve it properly. So far, he’s disconnected the supposed “earth” to the tiller shaft housing. Yet I still saw a little white cloud coming from the anodes in the rudder as the water came in. Not as active but still going.

Boat is not connected to shore power.

 

[GregOddity]

As others have said this is all wrong. There is no need for anodes where you have them - in fact you have created a problem by connecting the stainless skeg to the bronze cutless housing. Remove that and the anodes - they won't do anything as there are no mixed metals on your stainless rudder or the skeg.

Note you have a hull anode. What is this connected to? It should only be to the prop shaft to protect the prop on the stainless shaft. Remove any connections to the stern tube and through hulls. They do not need connecting to anodes.

Aware repeating advice, but just reinforcing the points. Exactly the same will happen again if you do not disconnect the bonding circuits because it is that which is the source of the problems.

Sadly, I get paid to fabricate as the owner wishes. I did offer an "opinion" but owner knows best and wanted it like it was before even after I mentioned that the "before" caused its rudder to drop off and melted everything.

Hull anode is connected to a supposed earth and engine. Nothing made much sense to me but the "old Guard" at the marina knows best and I keep quiet and do what I’m told. They all been "sailing" for 30 years of course.
However I’m listening with attention to your opinions here as I have my own circuits to make.

 

[Poey50]

You should read this, Greg.

http://coxeng.co.uk/metallurgy/electrolytic-corrosion/

Also Google the MAIB report on the sinking of Random Harvest.

 

[PaulRainbow]

Sadly, I get paid to fabricate as the owner wishes. I did offer an "opinion" but owner knows best and wanted it like it was before even after I mentioned that the "before" caused its rudder to drop off and melted everything.

Hull anode is connected to a supposed earth and engine. Nothing made much sense to me but the "old Guard" at the marina knows best and I keep quiet and do what I’m told. They all been "sailing" for 30 years of course.
However I’m listening with attention to your opinions here as I have my own circuits to make.

I refuse to carry out any work that i know or believe to be incorrect.

 

[GregOddity]

I refuse to carry out any work that i know or believe to be incorrect.

Paul, I also refuse to carry out any work that I know is incorrect, as anyone with a tiny bit of professional capacity would. Alas, I fail to see your point as I fabricated the Rudder and skeg thing.

My welding and fabrication are above standard, beyond reproach and well executed! It’s well welded, all angles and tolerances are true and I even corrected a wrong angle that was causing friction on the rudder bearing and was due to a factory misalignment on construction of the hull.

Can’t see what my welding has to do with electric currents on the boat. NOT being an expert on the matter as I clearly stated. I have no knowledge to impart if it is right or wrong to connect an anode to the Rudder or drill and tap an M8 hole for the owner to do HIS electrical installation as he sees fit and had been told by a marine electrician to do.

I posted here as an extreme example of what electrical currents can do to metal in a marine environment on a problem I found as a TIG WELDER.

I do MARINE WELDING and fabrication of Stainless steel 316

Here are some of my welds that have NOTHING to do with any galvanic or other forms of current except when I’m welding

 

[VicS]

As others have said this is all wrong. ........................
>
>
Aware repeating advice, but just reinforcing the points. Exactly the same will happen again if you do not disconnect the bonding circuits because it is that which is the source of the problems.

I do not believe the bonding circuits are the fundamental cause of the problems . On their own they may result in some galvanic corrosion or even corrosion due to stray currents in the water but the corrosion we see is so extensive and severe that it must be caused by electrolysis itself the result of an electrical defect. Maybe something incorrectly wired or maybe a fault which has occurred in otherwise correct wiring.

If all the bonding is removed the corrosion should become very localised and perhaps help identify the basic cause.

 

[VicS]

I have no dog on this race. ....................

It does look like the anodes are “electroplating” the surfaces around but it’s easy to see that I clearly mentioned anodes when I referenced “tin”. Obviously, I had not yet had my morning coffee and meant Zinc. But I blame it on old age and arthritis on the left pinkie..

What you are seeing is the freshly etched surface much like the appearance of the remains of the skeg when first removed from the water. The mild steel of course quickly started to rust . The new stainless steel will re-aquire a protective oxide film with little or no change in appearance.

 

[GregOddity]

I do not believe the bonding circuits are the fundamental cause of the problems . On their own they may result in some galvanic corrosion or even corrosion due to stray currents in the water but the corrosion we see is so extensive and severe that it must be caused by electrolysis itself the result of an electrical defect. Maybe something incorrectly wired or maybe a fault which has occurred in otherwise correct wiring.

If all the bonding is removed the corrosion should become very localised and perhaps help identify the basic cause.

You should read this, Greg.

Electrolytic corrosion

Also Google the MAIB report on the sinking of Random Harvest.

Thanks for the link. It does look like electrolysis damage on the LM as well

 

[PaulRainbow]

Paul, I also refuse to carry out any work that I know is incorrect, as anyone with a tiny bit of professional capacity would. Alas, I fail to see your point as I fabricated the Rudder and skeg thing.

My welding and fabrication are above standard, beyond reproach and well executed! It’s well welded, all angles and tolerances are true and I even corrected a wrong angle that was causing friction on the rudder bearing and was due to a factory misalignment on construction of the hull.

Can’t see what my welding has to do with electric currents on the boat. NOT being an expert on the matter as I clearly stated. I have no knowledge to impart if it is right or wrong to connect an anode to the Rudder or drill and tap an M8 hole for the owner to do HIS electrical installation as he sees fit and had been told by a marine electrician to do.

I posted here as an extreme example of what electrical currents can do to metal in a marine environment on a problem I found as a TIG WELDER.

I do MARINE WELDING and fabrication of Stainless steel 316

Here are some of my welds that have NOTHING to do with any galvanic or other forms of current except when I’m welding

I wasn't commenting on your welding Greg, i was replying to your comment "Sadly, I get paid to fabricate as the owner wishes. "

Of course, if you only did the welding that doesn't apply to you, but to the people that incorrectly installed the anodes, bonding circuits etc

 

[GregOddity]

What you are seeing is the freshly etched surface much like the appearance of the remains of the skeg when first removed from the water. The mild steel of course quickly started to rust . The new stainless steel will re-aquire a protective oxide film with little or no change in appearance.

It does look like there is current at work on the anodes. The little white clouds form as soon as the tide comes in and the water touches them. I can't be sure if it's the freshly applied 3 coats of anti-foul and 2 of primer that are being peeled off completely or it's somehow the zinc being deposited as the hull is also changing its colour to a silvery Gray shade. It does however look like all the paint is being stripped off and bare metal is showing. It also looks very active. And now that you called my attention to it, it does indeed look like electrolysis. I have never seen such violent action before therefore the reason for posting here. Thanks for your input. Much appreciated.

 

[GregOddity]

I wasn't commenting on your welding Greg, i was replying to your comment "Sadly, I get paid to fabricate as the owner wishes. "

Of course, if you only did the welding that doesn't apply to you, but to the people that incorrectly installed the anodes, bonding circuits etc

Sorry Paul, was a bit overboard. got a few things on my plate and it just spilled. ?

 

[PaulRainbow]

Sorry Paul, was a bit overboard. got a few things on my plate and it just spilled. ?

No problem Greg, apologies if it looked like i was criticising your welding.

 

[GregOddity]

No problem Greg, apologies if it looked like i was criticising your welding.

No worries Paul. all good really.