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Old 11-26-2016, 06:25 PM   #1
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Can loose zincs lodged in heat exchanger heads be safely chemically dissolved?

I have numerous "broken off" zincs loosely lodged in their respective heat exchanger heads on my Yanmar engines (four on each engine). Does anyone have any experience with safely chemically dissolving them without corroding the exchanger's metal components? Removing and reinstalling the heads to clear the zincs will be an absolute nightmare due to lack of physical access (very poor design layout).
Any feedback would be appreciated, but unfortunately, I think I already know the answer to my inquiry... but just incase, thanks anyway,
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Old 11-26-2016, 06:41 PM   #2
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It can be done, but it will take a long time and a lot of acid. Barnacle Buster and similar is great at dissolving a 1/16" layer of scale in heat exchanger tubes. But dissolving a 3/8-1/2" thick zinc will take a long time and probably will require agitation to break up the layer of sludge on the outside so the acid can dissolve the zinc.

Years and years ago I was working for a chemical cleaning company, and a paper mill wanted a couple of inches of scale removed from inside a pipe system. Dumb me sent a truck out and we circulated 10% by weight HCL (muriatic acid) through the pipe for 4 hours at 140 degrees. When we opened the pipe up, we had only removed a half inch or so of scale.

The mill ended up replacing the pipe rather than keep trying with acid.

David
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Old 11-26-2016, 07:16 PM   #3
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As D.M. says it will take a lot of acid. Best to open it up .
If you do go that route the cleaner must be circulated to remove the broken down stuff and circulate fresh cleaner past the zinc pieces.

How they are installed can affect them. I put a wee bit of sealer on the zinc threads and shoulder where the zinc butts against the brass head. I also use a wrench and pliers to snug the pencil zinc into the head. Stops or reduces the actual threads being eaten as that is a weak point.

In the future the zincs should be checked more often. Not all zincs will corrode away at the same rate so you need to check often enough to determine the life cycle of each zinc and that no more than ~50% is gone. May not stop all broken zincs problems but will reduce them a lot.

And be carefull as I believe some Yanmars may be touchy about this, just don't know which ones.
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Old 11-26-2016, 07:28 PM   #4
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Rydlyme will eat them up, and Not damage your components.
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Old 11-26-2016, 07:48 PM   #5
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I've had a few zincs break off over the years and I must confess I did absolutely nothing to get them out. I figured that they would dissolve over time. I have never had a problem. Perhaps I just got lucky but I chose to believe they. dissolved.
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Old 11-26-2016, 07:55 PM   #6
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I have been researching Rydlyme to run through the entire raw water system as a PM for scale. I also spoke to the corporate contact that supplies it.

I have not used it, but from what I understand it will eat up those zincs in a few hours. You need to recirc it, so getting a company that has the tank, pump, etc, and has done it would be the best way IMO.

Google their website for diagrams and more info.

If you do it, I would be interested to hear how it goes, and see some pics.
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Old 11-27-2016, 09:50 AM   #7
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Dissolve zincs

Barnacle Buster will do it in about 6 hrs
Remove your water pump impellers
Use their recirculating kit (5 gal bucket with a marsh pump inside)
Have had one for years now and works great
It's a good idea to do this anyway as maintenance on the coolers you would be surprised at the difference it makes in cooling
I also use it to clean my A/C units, it will drop the head pressure and make your system run much better. My A/C unit looked pretty clean but after cleaning my vent temp dropped by 7 deg!
Order direct from factory or on line, get the concentrate not the ready to use mix its about 1/3 the price compared to places like West Marine.
Ive personally used it on 2 different boats for over 12 years and it works as advertised.
Also great for cleaning sea strainers.
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Old 11-27-2016, 11:16 AM   #8
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some engines use many different metals, especially aluminum, and plastics so be careful with chemicals. IMO the only way you will know what's going on in the HE is to take it apart and do it right.
When I got my boat zincs were plugging parts of the tubes and seemed almost melted into place by corrosion.
Are there end plates to remove without removing the HE???
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Old 11-27-2016, 01:06 PM   #9
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From what I have read, the Rydlyme (and other brands) are completely safe with the typical metals on engines, and plastic. This fluid is not hazardous, and theoretically you can dump it in the ocean without causing harm. Again, no first hand experience, but based on the prelim research I did, and chatting on some other forums, thousands of owners do this type of cleaning on their boats. It also appears to be a common PM in the UK based on a forum over there.

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some engines use many different metals, especially aluminum, and plastics so be careful with chemicals. IMO the only way you will know what's going on in the HE is to take it apart and do it right.
When I got my boat zincs were plugging parts of the tubes and seemed almost melted into place by corrosion.
Are there end plates to remove without removing the HE???
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Old 11-27-2016, 02:28 PM   #10
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If Rydlyme or similar can dissolve a zinc, how can it be safe for typical metals on engines? And I can assure you that it will dissolve aluminum.

So only use it on raw water systems. These are made with bronze and cupronickel alloys which can withstand the corrosion ok. But only raw water systems. If you take an after cooler which has an aluminum housing for the air side and soak it in a vat of acid without removing the inner core and just soaking that, the housing will soon be gone.

Another story from my past: Years ago we tried cleaning fabricated stainless steel pipe by soaking in nitric acid which is fine for stainless steel. But the carbon steel sliding flanges were gone when we took it out of the nitric acid bath.

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Old 11-27-2016, 03:27 PM   #11
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Did I say to run it through the closed cooling system? The conversation from the beginning involved raw water systems. And yes, it is compatible with those systems.

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Originally Posted by djmarchand View Post
If Rydlyme or similar can dissolve a zinc, how can it be safe for typical metals on engines? And I can assure you that it will dissolve aluminum.

So only use it on raw water systems. These are made with bronze and cupronickel alloys which can withstand the corrosion ok. But only raw water systems. If you take an after cooler which has an aluminum housing for the air side and soak it in a vat of acid without removing the inner core and just soaking that, the housing will soon be gone.

Another story from my past: Years ago we tried cleaning fabricated stainless steel pipe by soaking in nitric acid which is fine for stainless steel. But the carbon steel sliding flanges were gone when we took it out of the nitric acid bath.

David
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Old 12-13-2016, 05:38 AM   #12
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Take all zincs off. Plug holes with the zinc bolts. Shut seacock and take raw water hose and put in a five gallon bucket with vinegar in it. Start engine and pump vinegar through engine. Let sit for 36 hours. Start engine and dissolved zincs plus a lot of corrosion will go out the exhaust.
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Old 12-13-2016, 06:58 AM   #13
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Our Yanmar 56HP wing engine had no zincs. I checked repeatedly with Yanmar and there were no zincs required in that model. The reason I mention this is because Yanmar stated zincs were not required because of the metallic composition of their water cooling system. Before you use any acid I would try to get confirmation from Yanmar that you will not damage the internals of your engine. My other (main) engine was a Cummins and built like a tank, so no hesitation with the acid approach if needed!!
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Old 12-15-2016, 09:05 AM   #14
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Maybe. Here is the most official process you will find.

1. Remove zincs, replace plugs and fill with appropriate acid (vinegar, ridlyme), etc.
2. Use the right amount of time for the acid, longer for weak vinegar, short for stronger acids.

Note: a weak acid over a long period of time can easily cause permanent damage, so don't underestimate the "safer" product.

3. Since you can't really see inside the heat exchanger, physically remove the end caps and inspect the outcome of the cleaning. If there are any remaining zinc pieces, you may easily remove them now.


Anyone who has not performed step 3 can not really tell you how effective the process is. Judge accordingly.

The more acid you use on a heat exchanger, the shorter it's life. The more clogged your heat exchanger, the shorter the life of your engine (potentially).



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Old 12-15-2016, 10:35 AM   #15
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If you want to know if your selected brew will dissolve a broken off zinc, try it in a bowl with a zinc as an experiment.

I like Dave am skeptical that a brew will attack a zinc aggressively enough to dissolve it yet will absolutely leave the critical alloys undamaged.

Many engines out there are running around with broken off zincs inside coolers. Find them all the time when servicing coolers. Usually cause zero harm. But in some cases the chunk abrades against the tube sheet and causes some wear. Still never seen a cooler fail due to this, but have seen them reported. Rare.
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Old 12-15-2016, 12:10 PM   #16
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Barnicle Buster

I have used Barnicle Buster in my Yanmar 4lhdte with great success. And yes I removed all of the coolers a year after using the Barnicle Buster just because the engine was 25 years old (salt water) and I needed a piece of mind. Heat Exchanger, Oil, and Air coolers were clean as could be. All of the rubber was in excellant shape. Looking back, there was no reason to remove and clean the components (after using the BB) other than to satisfy my curiosity.

Follow the directions. You can build your own bucket with a small bilge pump and some cheap hose.

As mentioned above a loose zinc or two won't cause any harm. I clean salt water side is much more important. (My engine does not have zincs either as an FYI.)
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