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Old 26-11-2011, 18:27   #1
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Unfreezing the Zinc Anode Plugs

I'm servicing my 25 year old Yanmar 2GM diesel, and want to replace the zinc anodes in the engine block as it is raw water cooled.

There are two anode plugs in the engine block, with the zinc anodes screwed in behind them. Both plugs are frozen /rusted? in and won't budge using a socket spanner with a reasonable amount of force / leverage.
I've sprayed them with a penetrating liquid too. I think I'll rip the motor off its mountings before these plugs come undone!

Also , one of the nuts in the plugs has been partially burred.

Three questions :
What is the best way to un-freeze the plugs;
Any tips on removing the burred head plug; and
Once the plugs are out, should I apply some sort of sealant on the thread (eg. teflon plumbers tape or grease) to help make removal easier in future?

Thanks
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Old 26-11-2011, 18:38   #2
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Re: Unfreezing the zinc anode plugs

I'm not sure about removing the anodes. Can you take a few pictures?

Hydrochloric acid will dissolve zinc, (as will any acid given enough time)...but HCl is obviously hazardous to work with.

A little Never-Seez or Tef-Gel will work fine for next time they have to be replaced. There will still be plenty of electrical contact. The engine mechanics at the yard use 3M 4200, which for them works fine. It's one of those things with more than one good solution.
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Old 26-11-2011, 20:26   #3
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Re: Unfreezing the zinc anode plugs

There is a product called Kroil. It is a penetrating oil but I have seen it work where other types did not. Give it time to work though. I have taken apart things that I wouldnt have bet a nickel on.

Not always easy to find. Depends where you are.
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Old 26-11-2011, 20:44   #4
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Re: Unfreezing the zinc anode plugs

Can you safely heat the metal around them with a propane torch? That will expand the female threads of the hole and allow you to back out the plug.
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Old 06-12-2011, 06:05   #5
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Re: Unfreezing the Zinc Anode Plugs

Many thanks for the suggestions.
I finally gave in to the problem and got the mechanic down, and he simply used a bigger lever on his socket spanner to get the plugs undone.

The prompt and considered advice that members so willingly share is what makes CF such an invaluable resource to our sailing / crusing community.
Kind regards,
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Old 06-12-2011, 06:51   #6
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Re: Unfreezing the Zinc Anode Plugs

When you put it back together do not use an Anti-Seize that is based on some metal (aluminum, copper etc.) in lubricants. You end up with Galvanic corrosion and it will make things worse. Use something like LanoCote.
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Old 23-06-2015, 05:09   #7
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Re: Unfreezing the Zinc Anode Plugs

Quote:
Originally Posted by CharlesFCook View Post
When you put it back together do not use an Anti-Seize that is based on some metal (aluminum, copper etc.) in lubricants. You end up with Galvanic corrosion and it will make things worse. Use something like LanoCote.
Yeah, I know this is a very old thread. I came across it while searching for info about engine anodes.

This advice seems contrary to standard practice; I have always had good results with stuff like Never Seez which does contain metals.

Perhaps I haven't kept up to date with best practice, has anyone else stopped using such anti-seize products and switched Lanocote?

Note, I do use Lanocote for some applications but I would default to Never Seez for engine nuts and bolts or Loctite if required.
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Old 25-06-2015, 17:39   #8
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Re: Unfreezing the Zinc Anode Plugs

No need to use anything usually. Should be able to tighten using medium force and, if checked every 3 to 6 months, should come out without much fuss.

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Old 25-06-2015, 17:47   #9
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Re: Unfreezing the Zinc Anode Plugs

Quote:
Originally Posted by Wotname View Post
Yeah, I know this is a very old thread. I came across it while searching for info about engine anodes.

This advice seems contrary to standard practice; I have always had good results with stuff like Never Seez which does contain metals.

Perhaps I haven't kept up to date with best practice, has anyone else stopped using such anti-seize products and switched Lanocote?

Note, I do use Lanocote for some applications but I would default to Never Seez for engine nuts and bolts or Loctite if required.
Geoff, I have used metal bearing anti seize for years and have never had any corrosion issues as a result. That said, I've switched mostly to anhydrous lanolin simply because it makes far less of a mess when I spread it around as i always seem to. Ann appreciates this...

And in the case of avoiding corrosion where s/s screws go into aluminium, I've always wondered if anti seize worked by some magic chemical process, or simply by excluding the salt water from the threads... as I think lanolin does. Any thoughts on that?

Jim
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Old 27-06-2015, 20:52   #10
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Re: Unfreezing the Zinc Anode Plugs

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Originally Posted by Jim Cate View Post
Geoff, I have used metal bearing anti seize for years and have never had any corrosion issues as a result. That said, I've switched mostly to anhydrous lanolin simply because it makes far less of a mess when I spread it around as i always seem to. Ann appreciates this...

And in the case of avoiding corrosion where s/s screws go into aluminium, I've always wondered if anti seize worked by some magic chemical process, or simply by excluding the salt water from the threads... as I think lanolin does. Any thoughts on that?

Jim
My main thought is that smarter people than me go to a lot of effort to make and then market products to prevent (limit?) corrosion especially between dissimilar metals. Some of these products must be snake oil but others appear to have stood the test of time, often without too much additional marketing efforts.

So I reckon those still around years later and used by most operators are probably working by some magic chemical process

Going back to first principles (which IMO, is a good place to start if one is not too knowledgable in any particular field) tells us that most (all?) metals will oxidise in the presence of oxygen i.e. air and dissimilar metals will do so faster due to galvanic action especially if in the presence of water.

This suggests keeping the air and water away from the metal is a good place to start and a grease like lanolin will do that for awhile. However the addition of sacrificial metals would seem to make sense. Choosing the right metal would assumably be dependant of the metal one is trying to protect. Like not using copper on aluminium!

Of course the above might be hogwash but until someone smarter provides a more creditable explanation of what to use or not use, I will keep using Duralac, Never Seez and similar.
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Old 27-06-2015, 20:54   #11
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Re: Unfreezing the Zinc Anode Plugs

And oh, Ann, you may be interested to know that some of us have to clean up whatever mess we make, all by ourselves!
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Old 28-06-2015, 02:31   #12
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Re: Unfreezing the Zinc Anode Plugs

The problem with most greases is that they biodegrade in the presence of salt water. I use a lanolin based one and it seems more resistant to this than the hydrocarbon based greases.

One of the most effective anti seizes I have used on threads around salt water is oil based paint. It dries and seals the water out without biodegrading. I suspect that this is the effective agency with the old barium chromate stuff we used on alloy when screwing stainless steel into it.

The mechanic did the right thing as spot heating any cast metal object is not considered prudent. Those plugs are big enough that with a six point socket and an extension you should be able to put an awful lot of torque on them.
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