Corrosion pundits - what about flushing with fresh water?

[Bacchus]

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)

 

[North Baltic sea]

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 Navalloy® 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

Navalloy® has a higher protection voltage than zinc.
Longer Life

Navalloy® lasts up to 30-50% longer than zinc.

 

[wwestman]

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.

 

[dhays]

Over the past few years I’ve 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 isn’t as clear that in practice a zinc anode creates problems in an engine that is fresh water flushed.

I’ve recently switched to fresh water flushing. I haven’t yet made the change to aluminum engine anodes. I like will at some point but I’m not terribly concerned about it.

 

[boatpoker]

Over the past few years I’ve 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 isn’t as clear that in practice a zinc anode creates problems in an engine that is fresh water flushed.

I’ve recently switched to fresh water flushing. I haven’t yet made the change to aluminum engine anodes. I like will at some point but I’m not terribly concerned about it.

Just to be clear, I never advocated one way or the other, just trying to keep the science straight.

 

[DDW]

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.

 

[boatpoker]

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.

 

[dhays]

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.

Don’t trust me, but I’ve heard that you don’t 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 engine’s electrolyte isn’t necessarily contiguous with the sea water.

Anyone actually know?

 

[boatpoker]

Don’t trust me, but I’ve heard that you don’t 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 engine’s electrolyte isn’t necessarily contiguous with the sea water.

Anyone actually know?

The anode is in the sea water path in the heat exchanger.

 

[dhays]

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.

 

[Juggerknot]

DDW and others,
Flushing your raw water side (often) with fresh water is a good way to help "stave off" marine age (basically the ravages of corrosion in the salt (air and water) environment that our salt water operated boats live in). If you flush regularly with fresh water (and store the raw water cooling side cleaned of salt water), you can greatly extend the time between having to fully service the various heat exchangers, gear coolers, aftercoolers, etc. and avoid the probability of overheating your engine (at least better of odds of doing so). Salt water in a hot environment (like inside our engine's components) will form a limestone like substance in the cooling passages which will only be removed (once hardened) by relatively aggressive measures like sending out to the rad shop for acid cleaning. Fresh water flushing will increase the time intervals between this type of (costly and/or time consuming) servicing. I just took apart my aftercooler for routine servicing (after 2 full seasons and about 400 engine hours) and there was no corrosion (even though the cooler consists of a "dog's breakfast" of dissimilar metals), and no calcium buildup at all. After properly reassembling with lots of grease, I can now leave this component for 4-5 years before servicing again, instead of having to look after it every 2-3 years. By the way, I service the cooling system more often than I could possibly "get away with", but I would rather be on the safe side. As far as zincs are concerned, I am certainly not an expert on this area, but I trust Tony Athens of Seaboard Marine. Unless I am reading his advice on this incorrectly, he says stay with zinc even if flushing with freshwater. His website has tons of great, free advice based on his training, education, and many years of experience. By the way, I am not associated in any way with him, or his business, just a grateful boater! His website is: sbmar.com.
Hope this info proves helpful,
Tom

I run a flush program using white vinegar and the a fresh water chaser. Cleans all the mineral deposits out oh h.e. and costs are nominal. No harsh chems or disposal issues either. Great for your fresh h2o system and water heater as well.

 

[DDW]

When you flush with vinegar, do you use full strength or a mix of fresh water?

 

[Juggerknot]

I flush with straight white vinegar, dissolves scale and deposits very well, great for flushing all h2o tankage, fresh and holding...

 

[geoleo]

The pink stuff has a lot of water in it, and is an electrolyte itself. It does not completely displace the existing water in the cooling system, but mixes with it. So the possibility of galvanic corrosion exists. While it does not seem to cause a problem with salt water boats and zinc anodes, or fresh water boats and magnesium anodes, the question remains what about fresh water boats and zinc anodes? I don't think there is a lot of collective experience there, as it is an unusual situation.

you may be 'over thinking' this a little