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Old 10-29-2018, 12:50 AM   #21
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I can't see how a fresh water flush would hurt, certainly. Where do you see Athens saying zinc even if flushed? Haven't found that in his stuff. I'd be interested in his thinking.
Sorry, but between his responses on forum inquiries and all of the material he has posted on his site, I cannot remember exactly where I read it. If you want to be sure of his opinion, either ask the question on his site's Cummins forum or send him a personal email. I am reasonably sure he will respond.
Not a definitive answer in and of itself, but my aftercooler was stored all last winter with a solution of salt away and freshwater in it (with zincs), it was run almost 400 hours over 2 seasons and when I just took it apart there was no corrosion at all and only a very tiny amount of calcium showing around some of the core tube openings. A very tiny amount. I also freshwater flushed the engine as often as I could during the summer season. By the way, the gear cooler looked very clean and corrosion free as well.
If nothing else, read Tony's advice on aftercooler maintenance. They can cost you pretty dearly if you don't do the maintenance.
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Old 11-02-2018, 01:40 PM   #22
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hmmm...flushing with fresh water, and aluminum anodes. i read the hype, so i tried aluminum anodes one time, and when we hauled out, i found prop and thru hull problems! so quickly went back to the zink anodes! [after some conversations with people smarter than me] as to freshwater flushing, i`ve been doing it for eons! have gotten friends to do it too...if our boat is going to sit for a week or more, it gets flushed! my cooler zinks last more than a yr! when i was commercial fishing, when the season was over at the end of november, we took them into lake union/fresh water for several weeks, to let the growth fall off the hull! all commercial boats have keel coolers, so it`s a closed system like car...clyde
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Old 11-02-2018, 02:28 PM   #23
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I added a system where I plug in the water hose from the dock and turn on a few valves and flush the engines/genset with water and then a soapy soultion.
Works well.
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Old 11-02-2018, 03:03 PM   #24
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Since I couldn't find aluminum anodes, I flushed with fresh water, then pink antifreeze, and went home.

I wonder what a solution of PG antifreeze and fresh water does to the galvanic series.
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Old 11-02-2018, 03:47 PM   #25
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Zinc anodes may or may not be effective in fresh water but it doesn't matter because if your boat is in Canada as mine is (Nova Scotia), you have to flush the system with the pink plumber's antifreeze - no option. Even salt water will freeze and burst a heat exchanger on the coldest days in winter in all parts of Canada except for BC. With regard to the fresh water flush which includes the main engine/generator heat exchanger, the muffler system (assuming a wet exhaust), and the feed line(s) to your dripless seal (assuming no stuffing box), there is definitely a benefit of getting the salt water out before you put in the plumber's antifreeze. On my boat that is a simple operation because I have my engine and generator plumbed into my freshwater tank so all I have to do is close the main raw water intake and open the fresh water supply valve and run tn the engine for a few minutes to clean out the system. I even do this numerous times throughout the summer if I know the boat is going to be laid up for more than a day or two. It greatly reduces internal corrosion and it takes about 2 minutes.

When pouring the plumber's antifreeze into your strainer, it's best to suck the salt water out of there first with a shop vac so the anitfreeze isn't initially diluted. Don't skimp on the antifreeze - pour at least 8-10 liters in there until red liquid can be seen coming out the exhaust and the around the prop shaft if you have a dripless seal. Don't forget to spray fogging oil into your air intake before you shut of the engine. Don't delay between these steps because you don't want your raw water impleller to run dry for more than a minute or so while you do the fogging. Your engine will then be properly pickled. Good luck.

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Old 11-02-2018, 04:11 PM   #26
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Zinc anodes may or may not be effective in fresh water
There is simply no question that zinc does not work in fresh water. The science is irrefutable.

The photo below shows a magnesium anode and a zinc anode on the same shaft after a season in the fresh water of Lake Ontario. The zinc anode clearly shows no galvanic effect while the magnesium shows definite galvanic corrosion.
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ZINC MAGNESIUM.JPG  
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Old 11-02-2018, 05:18 PM   #27
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I do not currently have a connection between fresh water tank and the flush fittings on the engine and genset. I think I may put them in, as it occurs to me it would make draining the fresh water tank much quicker. Also eliminate the need to get a hose to the engine room.

On the galvanic thing, the electrolyte makes a difference in what anode you use, e.g., fresh water vs. salt. So what's the right answer for PG? I guess I should have paid attention in chemistry class all those years ago but at the time it bored me to tears.
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Old 11-02-2018, 05:31 PM   #28
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Zinc anodes in fresh water

You may be right about Zinc not having the voltage potential to carry current in fresh water. This may be true when fresh water is defined as distilled water. The fresh water WE boat in has plenty of contaminants to carry a current. The evidence is the fact that I need to change my zincs every other year. I see them rot away just exactly as they did in salt water, albeit slower.
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Old 11-02-2018, 05:37 PM   #29
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The only thing I have been able to find so far is troubling: most of the info is from closed cooling loops, which are typically charged with a mixture of water and glycol (either ethylene or propylene). Dow in their literature cautions to avoid using galvanized metals in these systems, because in glycol the galvanic positions of steel and zinc are reversed, that is zinc becomes cathodic to steel. In plain language the steel corrodes to protect the zinc. Now these antifreezes have corrosion inhibiters in them, but again there are cautions that this will slow but not stop galvanic corrosion.
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Old 11-02-2018, 06:34 PM   #30
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You may be right about Zinc not having the voltage potential to carry current in fresh water. This may be true when fresh water is defined as distilled water. The fresh water WE boat in has plenty of contaminants to carry a current. The evidence is the fact that I need to change my zincs every other year. I see them rot away just exactly as they did in salt water, albeit slower.
Sorry, still wrong. Pure water is not conductive at all. Fresh water for the purpose of cathodic protection is neither defined as pure nor distilled water. All voltage potentials as measured for all cathodic protection systems are made with a range of contaminants normally found in lake water.

Suggest you study the NACE or ABYC Standards for cathodic protection which can explain all this in detail.
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Old 11-03-2018, 07:11 AM   #31
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I've seen exactly the same condition as the photo boatpoker posted except w 4 hull anodes on a friends boat. 2 alum and 2 zinc in a NY Finger Lake that has a relatively high salinity level for fresh water.
The alum anodes were functioning / corroding / eroding or what ever the correct term is?
While the zincs were smooth and basically unchanged after several yrs...
For those reporting zincs functioing due to clean / unclogged heat Xchgrs eg less calcification.... thats not the function of zincs as far as my limited knowledge?
Anodes of any type don't prevent calcium build up they prevent gslvanic corrosion different issues IMO unless I'm odf base (which is possible)
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Old 11-03-2018, 08:34 AM   #32
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Hi,

have you experience these anodes that fit all types of waters.

The performans metal anodes promise a lot, so I bought my groud anode for their plate anode for the next 2019. Here the water is really a little salty about 0.3-0.5% and zinc anodes work in brackish water I think well.

Snake oil or smart anodes?

https://performancemetals.com/

NBs


My new anodes
Performance Metals Navalloyģ aluminum anodes are manufactured to the military specification MIL-DTL 24779 and are suitable for use in all water types- salt, brackish or fresh.


The Only Anode That Works in All Types of Water

The aluminum alloy used in Navalloy anodes is very different from normal aluminum. It includes about 5% zinc and a trace of Indium, which prevents the build up of an oxide layer.
Aluminum anode alloy provides more protection and lasts longer than zinc. It will continue to work in freshwater and is safe for use in salt water. Aluminum is the only anode that is safe for all applications.
Better Protection

Navalloyģ has a higher protection voltage than zinc.
Longer Life

Navalloyģ lasts up to 30-50% longer than zinc.
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Old 11-03-2018, 10:26 AM   #33
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You cannot put two different types of anodes on the same piece of metal and expect anything other than the less noble to corrode first and fastest. Everything I have read says NOT to mix different types of anodes on the same boat or bonding system. Thus any "test" where the two anodes are not isolated from each other is invalid.
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Old 11-03-2018, 11:09 AM   #34
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Over the past few years Iíve been reading many of Tony Athens comments. I also recall several times where he has written that in his experience he has never seen problems in engines that use zinc anodes in engines that are fresh water flushed after use.

So while it is clear that boatpoker is correct that zinc anodes are not terribly effective on boats in fresh water, it isnít as clear that in practice a zinc anode creates problems in an engine that is fresh water flushed.

Iíve recently switched to fresh water flushing. I havenít yet made the change to aluminum engine anodes. I like will at some point but Iím not terribly concerned about it.
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Old 11-03-2018, 11:25 AM   #35
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Over the past few years Iíve been reading many of Tony Athens comments. I also recall several times where he has written that in his experience he has never seen problems in engines that use zinc anodes in engines that are fresh water flushed after use.

So while it is clear that boatpoker is correct that zinc anodes are not terribly effective on boats in fresh water, it isnít as clear that in practice a zinc anode creates problems in an engine that is fresh water flushed.

Iíve recently switched to fresh water flushing. I havenít yet made the change to aluminum engine anodes. I like will at some point but Iím not terribly concerned about it.
Just to be clear, I never advocated one way or the other, just trying to keep the science straight.
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Old 11-03-2018, 12:11 PM   #36
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I note that some engines (like my 6KW NL genset Shibaura engine) have no anodes at all.

I also don't believe you want to mix anode types on electrically connected equipment, so changing the engine would require changing also the prop anodes. Performance Metals does not make a prop nut anode. Can probably use another aluminum prop anode, but each proprietary alloy is slightly different in galvanic potential, so it's best to use the same.
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Old 11-03-2018, 12:55 PM   #37
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each proprietary alloy is slightly different in galvanic potential, so it's best to use the same.
Buy only mil.spec anodes and they will be the same. Avoid Chinese anodes like I avoid brussel sprouts.
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Old 11-03-2018, 04:19 PM   #38
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I note that some engines (like my 6KW NL genset Shibaura engine) have no anodes at all.

I also don't believe you want to mix anode types on electrically connected equipment, so changing the engine would require changing also the prop anodes. Performance Metals does not make a prop nut anode. Can probably use another aluminum prop anode, but each proprietary alloy is slightly different in galvanic potential, so it's best to use the same.


Donít trust me, but Iíve heard that you donít need to worry about using aluminum in the engine and zinc on the running gear. The reason, if I recall the rational, is that the engineís electrolyte isnít necessarily contiguous with the sea water.

Anyone actually know?
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Old 11-03-2018, 04:32 PM   #39
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Donít trust me, but Iíve heard that you donít need to worry about using aluminum in the engine and zinc on the running gear. The reason, if I recall the rational, is that the engineís electrolyte isnít necessarily contiguous with the sea water.

Anyone actually know?
The anode is in the sea water path in the heat exchanger.
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Old 11-03-2018, 04:49 PM   #40
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The anode is in the sea water path in the heat exchanger.
Makes sense.

I seem to recall that Cummins said it was OK to use zinc anodes in the engine even if aluminum is used on the running gear. I thought there was a service bulletin to that effect. However, my memory is terrible so I could easily be wrong.
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