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Old 04-24-2016, 07:40 AM
ArtJ ArtJ is online now
 
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Heat Exchanger Pencil Lead Fused!

The pencil lead in my MMI Exchanger would not come and broke off
leaving a wire core which broke off when trying to remove rest of zinc
I removed rest of zinc using flat screwdrivers to punch thru zinc
and ream it mostly free of zinc. then attempted to install new pencil
lead, but the bronze threads of the cap peeled off. The paassage
appears to have threads blocked with remains of old zinc and possibly
flattened from reaming with screwdriver. I bought a 3/8 npt tap
from Harbor Freight. I can't use torch due to proximity of
Fuel separator.

It was also suggested to not use tap as it could cut different threads
I bought a steel or cast plumbing plug of proper size as well.

Has anyone seen these weird Pencil Leads with a wire core?

Suggestions on how to proceed appreciated

Art
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Old 04-24-2016, 10:15 AM
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Art,

I had the exact same problem last spring. A zinc with a center wire that came apart. I cleared out the zinc remains, and had to re-tap the hole to get the new zinc in. But I started having overheating problems. Turns out that there was a lot more spent zinc crud still left inside. The only way to properly address it was to remove the end cap and clean out the HX. This is much easier if you can remove the HX from the boat. I pulled both end-caps, and flushed and rodded-out all the tubes. Really wasn't that hard. Replaced the rubber end-seals and rubber washers with new ones, and kept the old ones for emergency spares.

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Old 04-24-2016, 10:32 AM
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Question

What is meant by the term "spent" zinc?
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Old 04-24-2016, 11:57 AM
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Quote:
Originally Posted by edwardc View Post
Art,

I had the exact same problem last spring. A zinc with a center wire that came apart. I cleared out the zinc remains, and had to re-tap the hole to get the new zinc in. But I started having overheating problems. Turns out that there was a lot more spent zinc crud still left inside. The only way to properly address it was to remove the end cap and clean out the HX. This is much easier if you can remove the HX from the boat. I pulled both end-caps, and flushed and rodded-out all the tubes. Really wasn't that hard. Replaced the rubber end-seals and rubber washers with new ones, and kept the old ones for emergency spares.


Thanks

I believe that I may have used a cheaper zinc which had the wire in it
the source may have come from a on line discussion . I will only
buy zincs from trusted suppliers and test one by cutting it open
to make sure no wire.

The material the zinc was made of must be quite different than that normally used for Sacrifical Zincs and obviously not appropriate

Last edited by ArtJ; 04-24-2016 at 12:16 PM. Reason: Add comment
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Old 04-24-2016, 12:32 PM
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Quote:
Originally Posted by hanleyclifford View Post
What is meant by the term "spent" zinc?
The sacrificial zinc is more electrochemically active than bronze or stainless, so galvanic currents cause it to corrode, protecting the other metals.

The process of corrosion turns zinc into (primarily) zinc hydroxide [Zn(OH)2], which has a low solubility in water. This the grey-white "paste" you see collected at the bottom of the HX.
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Last edited by edwardc; 04-24-2016 at 12:35 PM.
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Old 04-24-2016, 12:45 PM
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Ed

Zincs normally dissolve, this one didn,t . The material must be different
such that Galvanic action deposited it, rather than disintegrated it.

Maybe even could deposit itself in the SW pump ??
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Old 04-24-2016, 01:06 PM
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This may be the source of these zincs

Home > Martyr Anodes 3/8 Dia Pencil Complete MTR-CME0
Martyr Anodes 3/8 Dia Pencil Complete MTR-CME0
Martyr Anodes MTR CME0
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Old 04-24-2016, 02:49 PM
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Bottom line:

Bottom Line : How do we recognize which type of Zincs are appropriate and which will cause harm??
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Old 04-24-2016, 06:19 PM
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Quote:
Originally Posted by ArtJ View Post
Bottom Line : How do we recognize which type of Zincs are appropriate and which will cause harm??
Don't know. I guess the easy answer is to buy them here!
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Old 04-24-2016, 07:09 PM
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Since these pencil zincs look just like the good ones, they need to be
identified as to source of origin, material composition( why they coat
surfaces )so that they can
be purged from all A4 stock, otherwise heat exchangers, plumbing
and possibly pumps are subject to damage.
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Old 04-24-2016, 10:32 PM
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This all starts to make some sense now.

I change my zinc every spring. Until about 3 years ago, I would go through about half of a (MMI) zinc in a season. The end would be cleanly gone, and there was no internal wire.

About that time, I found some inexpensive pencil zincs at a local chandlery and bought a pair.

Two years ago, when I removed the zinc, it was almost completely gone, leaving an internal wire exposed. I flushed things out as best as I could and installed a new zinc, but it went in with difficulty, and barely grabbed enough threads to seal.

One year ago, when I tried to remove the zinc, the cap twisted off, leaving the wire behind. I managed to grab and extract the wire (does this sound familiar, Art?) but the opening remained completely clogged. I managed to dislodge the crud with a screwdriver, and had to clean out the threads with a tap, but the new (MMI) zinc went in all the way. That's when I started overheating, and had to pull and clean the HX that you saw earlier. By the way, that HX cleaned up perfectly, with no damage or corrosion to the HX. It was just clogged up with a mix of gritty paste.

This spring, the zinc came out easily, with about half of the end cleanly gone and no internal wire in evidence!

Clearly, these "internal wire" zincs are of some alloy that leaves a much more solid corrosion product behind. I found a little information on "wire" vs "non-wire" types here:
http://www.rotometals.com/Pencil-Engine-Zincs-s/46.htm

I also found some comparison of Zinc Anodes vs Aluminum anodes here:
http://www.performancemetals.com/anodes/AnodeFAQs.shtml

The description makes me suspect that the "good" zincs that we want are actually made of aluminum!

As for determining if there's a wire inside, the only way I can think of that doesn't involve cutting one in half is to X-Ray it. (not practical unless you happen to be a dentist!)

It should be possible to tell Aluminum anodes from Zinc anodes by the weight. The Aluminum ones (actually an Aluminum/Zinc/Indium alloy called Navalloy) should be much lighter:
http://www.performancemetals.com/anodes/navalloy.shtml
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Old 04-25-2016, 09:14 AM
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Cut 2 open

I just cut the last 3/4 inch off 2 zincs.

Weight was similar

One I had and unsure if wire type , one new from WM.

Neither had the wire and weighed similar and both stamped Martyr .

In the past WM zincs had to be cut to length.

Unsure if Martyr also makes wire style as well
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Old 04-25-2016, 09:22 AM
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Have you considered contacting Martyr? If you do, maybe ask them if there is a preferred alloy for boats kept in estuaries (brackish water) where water salinity can vary greatly. Boston Harbor and the Chessy are both estuaries and I would expect the deeper into the bay, the lower the salinity.

From Performance Metals Products:
Quote:
Q. What anodes should I use in freshwater?

A. Where possible Navalloy™ (aluminum/zinc/indium alloy) anodes are recommended over zinc. Zinc anodes can become inactive after only a few months due to the build up of an insulating film of zinc hydroxide. Aluminum anodes will remain active. Don't take our word for it though, ABYC (American Boat and Yacht Council), who set the standards for the industry, clarified their recommendations on anode materials in the Standards and Technical Information Reports for Small Craft (July 2008-2009)
Name:  Anode type chart.jpg
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According to this information it's recommended you use aluminum based anodes given the areas you keep your boats.
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Old 04-25-2016, 01:46 PM
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Zinc has been used forever in mass and Cape Cod Never had problems
till now. BTW the pencils were not necessarily provided by Marytr SP


A good suggestion to call them Re: What's up with Pencils with WIRE core in them

Last edited by ArtJ; 04-25-2016 at 02:17 PM.
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Old 04-25-2016, 03:29 PM
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I don't doubt zincs have been used forever but the question is whether an aluminum based anode would be better for your waters. Performance Metals Products suggests it would and who knows, maybe Martyr would agree. Won't know until the question is asked.
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Old 04-25-2016, 05:11 PM
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I've been using Camp (a U.S. company) zincs for years, both for propeller shaft and heat exchanger (http://www.campcompany.com/home.php?cat=20). A couple years ago our local supplier stopped carrying Camp ("too expensive") and now carries Canada Metal "Martyr", made in China (http://www.martyranodes.com). They seem fine, so far. The heat exchanger pencil zinc appears to be solid metal, with no wire. The Canada Metal part numbers are the same as the Camp, except they start with CM. So the Camp pencil zinc E-1F (1/2" x 1-1/4") becomes the CME-1F. These dimensions are the O.D. and length of the anode only, not the pipe size of the brass plug.

Note that the pencil's thread and the plug's inside threads are a straight thread, not NPT. The plug's outside thread is NPT to screw into the heat exchanger.

Some places sell pencil zincs as one piece (plug and anode pencil), and some sell the pieces separately. I once worked for a boat builder who insisted on buying replacement anode pencils only, because he could save a few dollars per engine. If you're laying up 50 engines every fall, you can save a bit. Here is an example of what's left of a one year old Martyr 1-1/4" x 1/2" heat exchanger pencil zinc (CME-1F). It is shown unscrewed from its brass plug. The whole assembly costs $4.95. The anode itself is $1.99.
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Old 04-25-2016, 06:01 PM
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The Point

Quote:
Originally Posted by ndutton View Post
I don't doubt zincs have been used forever but the question is whether an aluminum based anode would be better for your waters. Performance Metals Products suggests it would and who knows, maybe Martyr would agree. Won't know until the question is asked.
The point is trying to identify the source and the problem with the
material used in the pencils WITH A IDENTIFIED METAL WIRE
CORE !! there has been no problem whatsoever with the Zinc based
pencils. Nothing to do with brackish water.

I have sent a email to Martyr
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Old 04-25-2016, 06:04 PM
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Exclamation

Replace every year? uh-oh!!!
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Old 04-25-2016, 07:22 PM
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Quote:
Originally Posted by ArtJ View Post
The point is trying to identify the source and the problem with the material used in the pencils WITH A IDENTIFIED METAL WIRE
CORE !! there has been no problem whatsoever with the Zinc based
pencils. Nothing to do with brackish water.

I have sent a email to Martyr
Well, I'm glad you contacted them and looking forward to their reply. It seems to me there's been a big assumption about a material difference rendering them dangerous and that somehow the wire you found is an indication of a substandard product when there's really no conclusive evidence just yet. About the wire, there may be a reason it's there, we just don't know so it may be a little early declaring it a problem. Ed's link to the Rotometals site discusses the wire pretty well and the reason it exists. Seems if you want the wire, get a Type C, if you don't, get a Type P.

About brackish estuary water, my point was going forward after this incident wouldn't you want to use anodes that offer the very best protection for the type of water you're in? I know I would.
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Old 04-25-2016, 08:32 PM
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Quote:
Originally Posted by edwardc View Post
The sacrificial zinc is more electrochemically active than bronze or stainless, so galvanic currents cause it to corrode, protecting the other metals.

The process of corrosion turns zinc into (primarily) zinc hydroxide [Zn(OH)2], which has a low solubility in water. This the grey-white "paste" you see collected at the bottom of the HX.
Thanks Ed. The subject of zincs in exchangers has always puzzled me. The exchanger itself being copper would seem to be noble enough to protect itself. The zinc actually sets up a galvanic cell where none previously exists (save only the possibility of the solder versus the copper). Against what is the exchanger actually being protected? I have exchangers on my boat with 25 years of service under their belts with never a zinc. Interesting quote attributed to John Westerbeke in the first sentence: https://books.google.com/books?id=oC...angers&f=false
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Old 04-25-2016, 08:51 PM
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I found this source for the Aluminum (Navalloy) pencil anodes:
http://www.go2marine.com/product/198...npt-plugs.html

And, just to muddy the waters further, note that it too has the central wire, which they call "Secure Core"!

I went to the boat today and pulled out my last spare zinc anode and examined it. It appears that the zinc rod is cut to length during manufacture, and at the right angle you can clearly see the end of the wire core in it! So at least it should be possible to non-destructively determine if a pencil zinc has a wire in it.
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Old 04-25-2016, 08:52 PM
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I had a diver tell me that my shaft zinc was fine and did not need replacement after 5 years in Florida salt water.

When I told him that it was 5 years he asked if I had a zinc in my heat exchanger. I told him yes, and he said that the exchanger zinc was probably eaten away.

not sure what to think of that.

Last time I had the exchanger out was 2009. The zinc was totally worn away. inside was a deposit on the end of the exchanger, right where the zinc was. It looked like the one pictured.

I had used a zinc purchased from WM.
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Old 04-25-2016, 09:04 PM
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It would seem that the "zinc" is already a three way party before it even gets installed - brass, zinc, and whatever the wire is made of. It would also seem the whole group would get eaten by the (copper) exchanger.
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Old 04-25-2016, 09:15 PM
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Maybe something to be learned here

Here are Defender's opening comments on anode selection:

Name:  Defender Anodes.jpg
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and this from BOAT US (bold face added for emphasis):

Quote:
In recent years cadmium in zinc has become an environmental concern, leading to a movement in the direction of aluminum anodes. Such anodes are effective even for protecting aluminum components--lower end cases, for example--because the aluminum used in the anode is a more anodic alloy. Aluminum alloy anodes are almost certainly to become more common. It has not happened already only because the cost of aluminum anodes has been higher than zinc without any discernible benefit to the boatowner. Today aluminum is actually cheaper than zinc. In addition, aluminum anodes tend to last longer, they work better than zinc in brackish water (and maybe in salt water as well) and they appear to be better for the environment. When making the switch from zinc to aluminum, ALL of your anodes must be aluminum. This can be a problem in some locales as many local marine suppliers still do not stock a wide selection of aluminum anodes. That will eventually change.
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Old 04-26-2016, 01:57 AM
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Quote:
Originally Posted by hanleyclifford View Post
The subject of zincs in exchangers has always puzzled me. The exchanger itself being copper would seem to be noble enough to protect itself. The zinc actually sets up a galvanic cell where none previously exists (save only the possibility of the solder versus the copper). Against what is the exchanger actually being protected? I have exchangers on my boat with 25 years of service under their belts with never a zinc. I
Yes.
Zinc is the sacrificial metal and copper has a lot more galvanic "pull" on zinc than almost anything.
Copper dismantles zinc which then turns into zinc hydroxide and can plug up the HX. Sometimes it gets rinsed or pushed out before it plugs up the HX. Sometimes not.
Try this sometime: Put a copper wire and a zinc galvanized nail with a wire on it into a lemon and touch both wires to the top of your tongue. Or if you don't want to go through the drill google "lemon battery".

TRUE GRIT
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