High Cost of Rhomar Exchange

@sequimite, from what I've read, that quote by Mark Turney is not correct. The confusion about the life cycle didn't come from finding that Rhomar did not perform better. It came about by someone using information from the European version that contains poisonous chemicals not allowed in the US. As far as I know, the US version never claimed five years, but regardless, the five year recommendation came from a different formulation.

Mark Turney's posts, although wordy, did not convince me that there are no differences between the two glycols. There are too many claims on the other side to make me believe that it's some kind of conspiracy. You'd think that Century would show testing that their glycol is the same as Rhomar if that were the case. Admittedly, it's science that I don't fully understand, but I put my trust in the manufacturers (nuCamp, Airstream, Truma, Alde ...) recommendation and made the switch.

Hi,  "If it is water molecules separating from the glycol mixture and squeezing into the crevices to cause the corrosion"   I don't believe (as I understand it)  is the  hypothesis (separating of water) of what Mr. Turney is saying.  He is saying  the area around the clamp contains a stagnant flow area where no "new fluid" passes.  In this area, the inhibitors get "used up" when they attach themselves to the aluminum and form a "protective skin". Eventially this protective layer breaks off as scale.  Then new or additional inhibitor is needed to replace where the scale broke off or is void of inhibitor    Because this area is a stagnant flow area, no new fluid with fresh inhibitor is getting into this stagnant area.  So eventially you are just left with a glycol/water mixture with no or reduced inhibitor which results in  corrosion.  In regards to why it may be beyond the clamp..I would believe once it starts at the clamp,   the corrosion process/chemical reaction  will continue to eat or destroy metal, small piece by small piece,   overwelming any inhibitors on the metal surface.  Similar to on a car that a painted surface will eventially get rusty once rust starts in a small area.

In his video, Mark says he's been collaborating with various specialists. I personally trust the information and it certainly matches with the relatively random behavior people have been reporting. I'm looking forward to part 2 for sure. 

@sequimite
I think if you follow the numerous threads through, you'll find that there didn't seem to be a common cause in "which individual Alde systems developed corrosion".
Made me think there may have been some procedure at the factory, that was performed on some Tabs, but not on others, that caused it. Maybe lubricating the hoses before installing or some such.

sequimite said:

.......
My gut says that previous problems are likely related more to poor adherence to maintenance intervals than which fluid is used.

Any thoughts?

I think a key issue missing in the video is the discussion on minerals (ions) in the water.  Pure water does not cause aluminum or aluminum alloys to corrode.  It's the dissolved ions in the water that create the electron exchange with the aluminum that results in aluminum converting to aluminum oxide (corrosion).  This is why corrosion is faster in salt water because there are more calcium and sodium ions in the water that can facilitate the chemical reaction of aluminum (alloys) converting to aluminum oxide.

With that said, the overall hypothesis is likely correct; water and mineral ions are getting deeper into the crevice between the hose and aluminum tube and not being protected by the corrosion inhibitors.  I'm wondering though if the prime driver in whether this happens more aggressively in some systems is the hardness of the water in the system.  Maybe Nucamp didn't always use distilled water when mixing with the glycol.

PS:  Note that in any solution (water with mineral ions or water with glycol) the molecules are generally already "separated" and free flowing.  Glycol molecules do not bond with water molecules.  If anything, molecules tend to separate in a solution, such as when you add salt (NaCl) to water which then becomes H2O with Na+ and Cl- ions.  

@pak, you can order those from Alde.   And you might check with nuCamp as I have heard that they will sell them if they have extras on hand.  You can also repurpose the old ones if they are only damaged at the ends.  I think I went through how I did that in that long War and Peace corrosion novel.  Let me know if you are interested in that and I'll track it down.

Any thoughts on the video saying that worm clamps are better than spring clamps? Everything I've read up to now has said the opposite, but Mark seems pretty insistent.

My biggest takeaway is that it may be best to use two spring clamps at the connections. One in the middle and one all the way at the edge to lessen the chance of penetration.

fstop32, thank you for the information and offer. I looked at mine this afternoon and they appear to be fine. Maybe this fall I will take the convectors out and treat the ends. I will looked into Mark's recommended product. I had been thinking about a 2 part epoxy for this purpose.

Well, that is very interesting and a great find.  I looked up the 5923 and here is what it says.  I also found the place in the 3010 manual where it says to use it as @tybladesmith says. Similar to what Mr. Turney suggests.  Wonder if Nucamp is using anything on their builds?  Does Alde still require it for the 3020?  Hmm..

@ScottG and @fstop32, you mentioned my use of heat shrink tubing on convector pipes, so I thought I'd provide the links below from two years ago with my photos & source of that & the coating fluid I used on the pipes.  I have to say, that heat shrink tubing was not my original idea*(see bottom for sources), but I had not seen anyone use it on Alde pipes before.  After cleaning corrosion off the pipes, I applied a silicone conformal coating fluid that is more commonly used for electronics & has a high temperature resistance.  I also used it to coat the circuit board inside the shunt of my Victron battery monitor to protect from corrosion (probably also good to have for other little boards that may be exposed to dampness).

Link to photo of installed 1" heat shrink tubing..
https://tab-rv.vanillacommunity.com/discussion/comment/167416/#Comment_167416
Source:
XHF 1 Inch (25mm) 3:1 Waterproof Heat Shrink Tubing Marine Grade Wire Cable Adhesive Lined Tube Insulation Seal Against Moisture Corrosion and Air Leakage, 4 Ft Black https://a.co/d/eG99BGt

Link to photo of coating fluid:
https://tab-rv.vanillacommunity.com/discussion/comment/167596/#Comment_167596
Source:
MG Chemicals - 422C-55MLCA 422C Silicone Conformal Coating 55 mL Bottle https://a.co/d/2nj98wZ

I should also mention that this particular heat shrink tubing has an adhesive coating on the inside that gives a very firm adhesion, yet is still removeable if needed.  I  tested that.
This spring will mark two years since I installed these & added a 3-way valve, so this year I'll be able to do a relatively painless fluid exchange (except that I hope to switch over to Rhomar), but still need to get the sources for it & the cleaner solution.  I would be very curious to see what the condition of my protective layers is when I change fluid in a few months, but not sure I want to have to redo my work.  My curiosity may get the best of me.  We'll see.

Mark's videos were interesting too, including the comparison of molecular sizes, although I  doubt that the corrosion depends on the confined spaces getting that tiny.  In the wider parts of those crevices between the hose & pipe, I would expect that you can still get crevice corrosion where the fluid doesn't get refreshed as it does in an unobstructed tube.  Fluid even flows fastest in the center of a tube as opposed to near the inside walls. This is true in blood vessels as well.  But, it is a convenient teaching tool to compare the size of molecules as another mechanism, and corrosion is likely worse in the smaller spaces anyway.  I still feel like the heat shrink tubing provides an additional layer of protection on top of a coating, or even without the coating, if the tubing has an inner adhesive.

*Edit:  First mentions of heat shrink tubing I saw, both from the Alde Corrosion discussion by members with professional experience dealing with corrosion..
1st:  (by @rh5555 )
https://tab-rv.vanillacommunity.com/discussion/comment/166597/#Comment_166597
2nd:  (by @BridgerSunset )
https://tab-rv.vanillacommunity.com/discussion/comment/167341/#Comment_167341