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Old 12-02-2020, 17:17   #1
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anode corrosion

Our saildrive anode was replaced in mid October. Yesterday we found the anode completely powderised. The prop anode and the bowthruster anodes are OK. We have been in a marina for this time. One neighboring boat has a similar situation. That owner is away so we do not know how old that anode is. Anodes have lasted 12mths in the past.
Where do we start.
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Old 12-02-2020, 19:12   #2
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Re: anode corrosion

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Originally Posted by jaramanpotter View Post
Our saildrive anode was replaced in mid October. Yesterday we found the anode completely powderised. The prop anode and the bowthruster anodes are OK. We have been in a marina for this time. One neighboring boat has a similar situation. That owner is away so we do not know how old that anode is. Anodes have lasted 12mths in the past.
Where do we start.

Then your anode is overloaded

Make sure that your engine is electrical isolated...no+ and no - on the engine

Copper oxide antifoul is a very poor choice for modern plastic boats. The copper overloads the anodes, destroys rudder bearings and sail drives
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Old 12-02-2020, 19:28   #3
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Re: anode corrosion

Recently antifouled with Micron Extra 2
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Old 12-02-2020, 19:33   #4
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Re: anode corrosion

Saildrive has Trilux antifoul paint as always. Thanks for your input.
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Old 13-02-2020, 00:11   #5
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Re: anode corrosion

Quote:
Copper oxide antifoul is a very poor choice for modern plastic boats. The copper overloads the anodes, destroys rudder bearings and sail drives
That seems an odd statement. What is different about "modern plastic boats" that causes this phenomenon? And how new must a boat be to require some other form of anti foul paint? And how does copper oxide attack my bronze rudder bearings?

No argument that copper based paints should not be applied to saildrive housings... that's a no-brainer, but not what the OP is on about.

The vast majority of "modern plastic boats" use copper oxide based anti fouling. Perhaps you could advise them of a better alternative.

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Old 13-02-2020, 00:19   #6
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Re: anode corrosion

Is it a zinc anode in salt water? Is the prop anode also zinc?
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Old 13-02-2020, 01:09   #7
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Re: anode corrosion

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Then your anode is overloaded

Make sure that your engine is electrical isolated...no+ and no - on the engine

Copper oxide antifoul is a very poor choice for modern plastic boats. The copper overloads the anodes, destroys rudder bearings and sail drives
Yanmar requires the engine and saildrive be bonded
Volvo requires they NOT be bonded.

Hopefully the OP did not paint his drive with anti-foul
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Old 13-02-2020, 01:35   #8
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Re: anode corrosion

[QUOTE=Jim Cate;3073524]That seems an odd statement. What is different about "modern plastic boats" that causes this phenomenon? And how new must a boat be to require some other form of anti foul paint? And how does copper oxide attack my bronze rudder bearings?

No argument that copper based paints should not be applied to saildrive housings... that's a no-brainer, but not what the OP is on about.

The vast majority of "modern plastic boats" use copper oxide based anti fouling. Perhaps you could advise them of a better alternative.




Modern boats are sailing with aluminum rudder stocks, aluminum lower rudder bearings and aluminum sail drive legs


All this aluminum is wet ,submerged in an electrolyte

When you use copper oxide antifoul you have essentially built your boat out of copper

This copper overloads the anodes and attacks wet aluminum , galvanic action

This is The reason you void the warranty on a Saildrive leg when you use copper oxide

https://www.yanmar.com/us/wp-content...-Corrosion.pdf

Service bulletin Yanmar “ do not use copper oxide antifoul on the BOTTOM OF THE BOAT “
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Old 13-02-2020, 01:52   #9
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Re: anode corrosion

Quote:
Originally Posted by jaramanpotter View Post
Our saildrive anode was replaced in mid October. Yesterday we found the anode completely powderised. The prop anode and the bowthruster anodes are OK. We have been in a marina for this time. One neighboring boat has a similar situation. That owner is away so we do not know how old that anode is. Anodes have lasted 12mths in the past.
Where do we start.

It is possible ts is stray currnet corrosion caused by a poor earth in the marina power sytem, I have heard of that in other marinas when long distance sailing.
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Old 13-02-2020, 09:40   #10
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Re: anode corrosion

Your first line of defense is a galvanic isolator in your shore power connection to isolate you from dock voltages and electrically aggressive neighbors.

With natural Aluminum to salt water DC voltages as high as 0.9 volts it only takes 0.15 volts of AC leakage to carry DC through a 1.2 volt isolator and eat zincs for breakfast.
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Old 13-02-2020, 20:43   #11
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Re: anode corrosion

Recommend you hire a qualified corrosion tech to perform a corrosion survey on your boat. The condition that you asked about is common but the remedy won't be found without a knowledgeable tech performing the survey.
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Old 13-02-2020, 22:48   #12
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Re: anode corrosion

[QUOTE=slug;3073547]
Quote:
Originally Posted by Jim Cate View Post
That seems an odd statement. What is different about "modern plastic boats" that causes this phenomenon? And how new must a boat be to require some other form of anti foul paint? And how does copper oxide attack my bronze rudder bearings?

No argument that copper based paints should not be applied to saildrive housings... that's a no-brainer, but not what the OP is on about.

The vast majority of "modern plastic boats" use copper oxide based anti fouling. Perhaps you could advise them of a better alternative.




Modern boats are sailing with aluminum rudder stocks, aluminum lower rudder bearings and aluminum sail drive legs

I'd say a few modern boats are thus constructed, Hanse being one. But there are plenty of better constructed modern boats that have stainless rudder posts, bronze bearings and even s/s shaft drives. Here in Oz, the Hanse dealer in Pittwater uses copper based paints, except around the sail drive and the rudder penetration and blade. In those areas they apply one of the sadly ineffective non-copper paints available.


All this aluminum is wet ,submerged in an electrolyte

When you use copper oxide antifoul you have essentially built your boat out of copper

This copper overloads the anodes and attacks wet aluminum , galvanic action

This is The reason you void the warranty on a Saildrive leg when you use copper oxide

https://www.yanmar.com/us/wp-content...-Corrosion.pdf

Service bulletin Yanmar do not use copper oxide antifoul on the BOTTOM OF THE BOAT
Unfortunately your link does not work for me... I'd like to see what they say.
But if the prohibition of copper based paints applies to all boats with sail drives, it is just another serious reason to not have one in your boat. We all know that one does not use copper directly on the saildrive or nearby, but this is the first time I've seen the whole bottom denied useful antifoul.

Jim
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Old 13-02-2020, 22:58   #13
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Re: anode corrosion

On our steel boat, the hull and rudder were first coated with an epoxy barrier coat that provides electrical insulation from the base metal. Copper anti-foul can then be applied over it.

HINT, the anti-foul coat(s) has to be applied within 48 hours of the epoxy coat. If the epoxy is allowed to set up any longer it gets a hard glossy finish that the anti-foul won't stick to, so it comes off in big sheets a week after you put to sea. Don't ask me how I know THIS!
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Old 14-02-2020, 00:27   #14
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Re: anode corrosion

[QUOTE=Jim Cate;3074167]
Quote:
Originally Posted by slug View Post

Unfortunately your link does not work for me... I'd like to see what they say.
But if the prohibition of copper based paints applies to all boats with sail drives, it is just another serious reason to not have one in your boat. We all know that one does not use copper directly on the saildrive or nearby, but this is the first time I've seen the whole bottom denied useful antifoul.

Jim
To reduce the load applied to anodes and underwater
Metal do not use copper oxide paint
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