Kopr Shield Conductive Grease or Never Seize?

[Blitz]

I recently read a article in Sail magazine about tools you should have on a boat and it noted that the product Kopr Shield is a "conductive grease for battery connections and to seal engine zincs."

I have a Yanmar 3GMD on my boat and it is a raw water cooled engine that has two plugs in the side of the engine block and one at the end of the head that when removed the zincs (pencil type) can be checked/replaced. After having trouble years ago getting these threaded plugs out of the head and engine block I have always made it a habit to use Never Seize on the threads and it has been much easier for removal. I was wondering if I should be using a more conductive grease or if it matters much. My zincs don't corrode much and most years they don't need replacing, but never have.

Any thoughts?

 

[dlochner]

I was just reading an article on Practical Sailor about anti-seize. Here's the link: https://www.practical-sailor.com/issues/44_7/features/Anti-Seize-Coatings-for-Spars_12448-1.html

It is however for subscribers.

The zincs don't have much to do with bolts on the engine. Heat is an issue. P-S was neutral on Boston's Never Seize. They liked Loctite LB 8023.

 

[Charles Erwin]

Yanmar expects these zincs to go 500 hours.

They will not waste much in the winter especially if you drain your motor and use antifreeze during layup. This rather slow rate of zinc degradation happens because the metals collection that make up the motor and that are exposed to cooling water are galvanically pretty similar. The normal aluminum, or nickel anti-seize compounds are fairly conductive but thread engagement wipes them off anyway so they have almost no measurable influence on internal mounted zinc decay rates.

Charles

ps I would use copper based on heat exchanger zincs because the exhangers are largely copper but not cast iron - which is your case.

 

[thinwater]

Conductive greases have NO FUNCTION at low voltages. This is pure myth and I challenge anyone to post data that shows they help (I would love to read the data--I've looked for and asked vendors for it). Second, any product that contains dissimilar metals can increase corrosion in a marine environment. Thus, if you are going to use an anti-seize where there is seawater, it must be a marine formulation. Kopr-Shield, for example, has performed poorly in many applications. Sail Mag simply didn't do the research, they went with conventional knowledge.

There are metals-containing greases for aluminum wiring. You will see it in your home entrance box. But it is serving a different function in a different environment. It is aluminum-specific. Not marine.

A very hot, dry environment, like manifold bolts on an engine, is totally different. The copper provides valuable high temperature anti-seize functionality there. This is where it earned the reputation, good stuff. But not for wet environments.

 

[Blitz]

Yanmar expects these zincs to go 500 hours.

They will not waste much in the winter especially if you drain your motor and use antifreeze during layup. This rather slow rate of zinc degradation happens because the metals collection that make up the motor and that are exposed to cooling water are galvanically pretty similar. The normal aluminum, or nickel anti-seize compounds are fairly conductive and thread engagement wipes them off anyway so they have almost no measurable influence on internal mounted zinc decay rates.

Charles

ps I would use copper based on heat exchanger zincs because the exhangers are largely copper but not cast iron - which is your case.

Thanks Charles, good to know the low rate of degradation is sort of normal. Also, no heat exchanger on this 1983 yanmar 3GMD - just raw salt water in the summer, and yes as you've guessed antifreeze during the winter layup.

 

[Blitz]

Thus, if you are going to use an anti-seize where there is seawater, it must be a marine formulation. Kopr-Shield, for example, has performed poorly in many applications. Sail Mag simply didn't do the research, they went with conventional knowledge.

Thinwater - what you you suggest?

 

[njlarry]

So on ss screws on aluminum masts, tef gel, locktight, anti seize or something else?

 

[Maine Sail]

Second, any product that contains dissimilar metals can increase corrosion in a marine environment.

Bingo!

The worst offenders are the ones containing graphite as graphite/carbon is at the extremely noble end of the galvanic scale. Heck even graphite packing and PSS carbon rotors increase the rate at which your anodes erode.

 

[jibes138]

In the aerospace industry we often specified zinc chromate primer for inserting helical inserts into aluminum housings. We also used Mo-Lith #2 on the screws for anti seize. Conductive grease or not at the atomic level when screws are torqued the surface imperfections in the metal scrape together and assure metal to metal contact. The surface finish will deform elastically until more and more surface is in contact to support the forces with sufficient area. I know aerospace is not a marine environment. Tell that to the guys maintaining F14's, F18's, E2's, etc.

 

[jibes138]

https://www.lubriplate.com/PDFs/PDS/3_16-Mo-Lith-No-2.aspx

 

[jibes138]

https://en.m.wikipedia.org/wiki/Zinc_chromate

 

[thinwater]

I'm sure you you've all heard of Tefgel. I've used good water proof grease, No-Ox-Id, and Lanocote with good success for these things. Just not anything with copper or, as Mainesail added, graphite. He's right, graphite packing does some interesting things. Aluminum next to carbon fiber is fun to watch.

 

[dlochner]

Aluminum next to carbon fiber is fun to watch.

Only a chemist would think so.

 

[JamesG161]

My zincs don't corrode much and most years they don't need replacing, but never have.

Do you have submerged shaft Zincs that are electrically connected to the Engine through the shaft?
If, Yes...
Your Pencil Zinc is just secondary or backups.
It is a GOOD thing that they don't sacrifice.
_____
I use Teflon tape on my Yanmar driven, Genset pencil Zincs and That Zinc does Sacrifice.
You know why?
If you put just a slight torque on the Pencil Zinc bolt, that torque forces a contact "metal to metal".
The galvanic electrical current flow is so small, that it doesn't take a lot of contact "metal to metal" to protect.

Anti Seize "stuff" is used to reduce the friction HEAT generated on Bolt Insertion, as you apply huge thread to thread forces.

Other reasons for not being able to remove that pencil Zinc would be from the Outside Environment.
Jim...

PS: Properly Torqued bolts actually "Stretch" the bolt with tensional forces to provide a seal. Forces in the order of Thousands of pounds per square inch are needed to stretch Steel.

 

[Charles Erwin]

Practically speaking external anodes are not in the same electrolyte as the internal. The only path between them is via the cooling water intake - which is itself largely insulated by the cooling water pump impeller. Also the voltage difference is so low and the intake so small in cross section the current density produced by the shaft mounted zinc is just about nothing measured any place within the internal cooling chambers of the motor. I doubt you could measure anything. External zinc anodes do not contribute protection to the internal surface of this rather corrosion resistant cast iron block recipe. If they did then Yanmar would not engage in all tooling and machining necessary for mounting internal ones.

As to internally mounted zinc anodes the cast iron motor block is too close - galvanically speaking - to produce anything but rather slow anode wasting.

Charles

 

[JamesG161]

I will reserve any further feedback on internal seawater exposure to Galvanic protection to just a simple observation...
Oh my Volvo Penta, there are NO locations spots for ANY engine Zinc, nor any mentions of them on the Volvo Penta Repair/Service Manual or Owner Maintenance Manual! Wait... not ! but Period.

I guess the Britts have figured it out.
Jim...

 

[Charles Erwin]

Internal anodes are found only in the seawater cooled versions of these motors. These Yanmar motors are not sleeved so I can only think Yanmar is trying to protect the head gasket - which is steel with a coating that probably contains a good bit of graphite. For that matter I ran an AQ 130 Volvo Penta (sea water cooled) gas motor in my ocean salmon boat for years and Volvo provided no anode at all. Cast iron is very corrosion resistant.

However - as you say with Volvo - I do not recollect anodes in any fresh water (antifreeze cooled) Yanmar either. The copper alloys used to build the exhangers are very corrosion resistant for sure. I still think it is a good idea to protect the seawater side of a heat exchanger or keel cooler and aftermarket custom exchanger builders do provide anodes in exchangers and keel coolers. Manufacturers rarely do.

Charles