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post #1 of 21 Old 06-11-2007 Thread Starter
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Galvanic corrosion inside winch

Hi there!

When opening my winch (Enkes 18), I had a bad surprise:


At the alu-stainless joint of the axis (the part in which you stick your winch handle, -part #3 on this drawing-), the aluminium is badly corroded.
The hole on the picture is the drain that flushes water from inside the axis, which is stupid because it drains the water between the axis and the bronze stand, keeping the water in the joint, thus increasing the corrosion.
My plan is to grind a "gutter" in the stainless part just below the aluminium drain to the bottom of the stainless part, so water will be flushed oustide the winch quickly.

But before doing so, does anyone has a better idea?

I have read the article here on Sailnet about galvanic corrosion and a zinc anode should fix the problem. But where do I place the anode? on the stainless or the aluminium... or both?

In last resort, I will go to a machine shop and have a 100% stainless axis made.

Thank you for your input!
Marc
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post #2 of 21 Old 06-11-2007
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Marc-

You can't really use a zinc in the case of something like this. You're much better off using a galvanic isolation washer made of thin plastic or galvanic isolation compound, like Lanocote or TefGel. I wouldn't go cutting grooves in the stainless part, as it might be used as a bearing surface to some degree. Cutting a gutter in it would drastically increase the wear on whatever part rotates on it.

If you are really having a problem with it... why not get the part made up by a machine shop in all stainless or all marine bronze (which is considerably easier to machine IMHO).

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SailingDog,
Today, I went to a machine shop and got a quote for the job: 600$. For that price, I'd better be getting a new winch...

Putting a washer in the joint is impossible. The aluminium is fixed to the stainless bottom. I have no idea on how to seperate them. Boat will be in water in 2 weeks, so I cannot afford to break the winch and have a non-funtionning winch on board.

I have been suggested to put some zinc powder (ultra fine) in the grease instead of a full anode, so the aluminium will be protected. Would that work?

Marc
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post #4 of 21 Old 06-11-2007
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No. Zinc need to make an electrical conection to the part that is being eatin.
Can you buy a new part from the company that built the winch?
how old is it? if it lasted a long time and is cheap to replace get a new part.
Just a thought

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post #5 of 21 Old 06-12-2007
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Try coating it with tefgel or lanocote, to prevent the water from affecting the aluminum. It works pretty well... so it is definitely worth giving it a shot.

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Soul Searcher,
The brand is Enkes and it comes from Netherland. Ordering a new part would be a good solution, but importing it would take long I think. The shaft isn't broken so I do not need an urgent replacement. They are 23 years old, so I just wanted to slow the corrosion to make them last longer!

Sailingdog,
I will give it a try!

Thank you for your time!
Marc
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post #7 of 21 Old 06-12-2007
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Quote:
Originally Posted by soul searcher
No. Zinc need to make an electrical conection to the part that is being eatin.
Can you buy a new part from the company that built the winch?
how old is it? if it lasted a long time and is cheap to replace get a new part.
Just a thought
I know next to nothing about it but this has me thinking.
Vasaline is a conductor af electricity.Unlike grease.How about zink powder in vasaline?
Mark
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Quote:
Originally Posted by travler37
I know next to nothing about it but this has me thinking.
Vasaline is a conductor af electricity.Unlike grease.How about zink powder in vasaline?
Mark
Ummm... Vaseline, which is Petrolatum Jelly, is not a conductor of electricity.

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post #9 of 21 Old 06-12-2007
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To grease it, use a silicone lubricant. I have had several winches apart and corrosion was never an issue. You may want to (silicone) those inferior jobbies up and then save for some better "sea going, non corrosion types"
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Vaseline, aka white petroleum jelly, IS a conductor. A poor one, but enough to create leakage current at battery terminals.

If I was going to potch around with Vaseline and zinc dust (and fine dust isn't cheap) I'd use antiseize instead. That's petroleum based oil loaded with copper, nickel, and other metal dust and it is effectively a decent conductor. It might protect the two metals as a sacrificial compound.

Putting aluminum and steel together that way in a marine part is simply defective engineering. If that is all one cylinder with just the machining we see at the bottom end...I'd try to shop around for a less expensive machine shop, and have a new part made up all from one metal--compatible with whatever the rest of the winch body is. I wonder if they could fab it from bronze instead of stainless, and still get sufficient strength and save something at the same time?
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