High Cost of Rhomar Exchange

AnOldUR

@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.

Freespirit

@sequimite, I will not comment on the pros or cons between the two products, but in my case we had bulges in less than a year on our new TAB. Bought it new October 2020 and noticed bulges in November of 2021. The bulges had to be forming in our first 12 months of ownership. 

ScottG

Having discussed the Alde corrosion issue ad nauseam on this forum, I concur that there did not seem to be a strong correlation between corrosion of the convector stubs (including the relative degree of corrosion), the age of the camper, or the extent to which maintenance was deferred. I suspect amount of use may be an issue, but have limited data in that regard.

I suppose time will tell if the Rhomer product is better at preventing this issue, but the recommendation in the U.S. has always been for a two-year exchange cycle, regardless of which brand of glycol is used.

Slackers

Rhomar is said to have a different corrosion inhibitor mix than Century.  NuCamp was not recommending the switch for older trailers like ours but lots of folks on this forum have done so. My fluid was due for a switch last summer and I chose to stick with Century.  Also note Mark on the YouTube channel added a ground wire to his tank in hopes of dealing with some corrosion issues related to the fluid and the copper drain tubes he installed.  Though I haven't done the ground wire, it seems like an easy thing to do for added peace of mind.

bergger

Here is a video he just did and it makes sense to me.  It also seems to confirm or at least go along with suspicions I have had on why only the exterior of the convector connections seem to corrode.  I felt it had to do with trapped fluid but his video seems to explain or give a theory as to why the trapped fluid on the connectors is causing the corrosion.  Maybe it is not so much the type of fluid but more so the design of the connections that cause the issue leading to the corrosion and that some trailers are routed or connected with just enough difference to cause the issue where others do not have it. 

https://www.youtube.com/watch?v=_0mRXz9m-5s

Dutch061

@bergger, thanks for sharing this. I believe this is very plausible and most likely the root cause. If so, changing fluid, adding grounds, sacrificial anodes, or standing on your head will not prevent it from happening. I believe at one time, NuCamp was using "dope" on the fittings to help prevent leaks. It is possible that this dope has helped to prevent corrosion on some units. Maybe not, maybe some are just luckier than others? 

Since I no longer have my 400, this is not a concern anymore.

Safe travels,

Brad

ScottG

I've always thought the "crevice corrosion" hypothesis previously discussed here was the most plausible explanation for this phenomenon. What Mark's video does is provide a plausible explanation of exactly why that crevice corrosion occurs. It seems to connect all the dots, even to the point of explaining why the corrosion does not seem strongly correlated with time, maintenance, or use.

I can't find his referenced Part 2 video, though--the one that is supposed to offer strategies for mitigating the problem. Anybody know the status of that?

I'm thinking some of the approaches previously suggested by @BrianZ (sealing the convector stub surfaces with heat shrink tubing, double-clamping the hoses, etc.) are probably the most likely DIY candidates for at least a partial solution.

Maple_Geek

Mark has not released the part2 YouTube video yet. Part1 was released yesterday.

ScottG

Ahhh, well, that would explain it! I shall stand by patiently...  :-)

AnOldUR

If it is water molecules separating from the glycol mixture and squeezing into the crevices to cause the corrosion, why does the corrosion extend beyond the clamp in this picture from the video? If water were passing the clamp, wouldn't we see other evidence of the leakage?

Yoshi_TAB

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.

AnOldUR

Yoshi_TAB said:

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.

This is all above my education level, but my understanding was that he said "... a (smaller) water molecule can get way down in here ..." but the inhibitor molecule are much larger and won't fit so the water molecules are able to corrode the aluminum. Maybe I misunderstood.

The different components of the glycol mixture don't separate when stagnant sitting in the jug. I'm having a hard time visualizing this happening within the Alde system. I'd think that it is a fairly stable mixture. I'm not saying that he's wrong, but it would be nice to see some outside collaboration.

I wonder if air bubbles in the system could get trapped in that gap and provide the oxygen for corrosion.

Maple_Geek

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. 

Yoshi_TAB

Hi, I see what you are saying..yes, he did say the water and glycol can seperate, but I don't think that can just happen on its own (IMO).  That seperation process requires "some force" from chemical processing and specialize equipment.  It's possible heat may be able to do, but unlikely.   The depeletion of the inhibitor in the stagnant area makes sense to me, but not the separation.   Most glycols and water (you can look them up) are what they call miscible in each other which means they can not seperate on their own.  I certainly think he is on to something and appeciate his efforts to the community.  R/

ChanW

@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?

Denny16

Our 2018 TaB400 has no sign of corrosion, it went almost 3 years before it’s first Century TF fluid change, and now is coming up on its next 2-year exchange, during which we will switch to the new Rhomar fluid, as recommended by nüCamp last year.  We do not have a corrosion issue and we do not want one.  It appears the new Rhomar fluid is better at preventing corrosion.
 Cheers 

Horigan

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

Part 2 of the maintenance video dropped a couple of hours ago. Has anyone located a source for convectors? Thank you

fstop32

@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.

fstop32

I watched the Part 2 video and the biggest tip I found was the coating material he painted the ends of the aluminum convectors and unions with to protect the aluminum under any tubing.
How the corrosion was getting started under the hose connections made sense.  I can't help but think the tool marks I found on the convector ends from the factory also created a nice little pocket under the hoses.  I wonder if Alde still cuts their aluminum tubing the same way?

AnOldUR

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.

Yoshi_TAB

Hi, 

I tend to agree with you in regards to the clamps.  He said the only reason why they are used is because they are fast and easy to put on and off.  While that may be true, I think there are good technical reasons of why spring clamps are used; (1) spring clamps  apply a more even pressure, (2)  the screw portion of worm clamps do loosen up after a while and (3)  as hoses shrink/dry  with time, a spring clamp can continue to apply pressure while a worm clamp has to be retighten.

 As I have mentioned, I do very much appreciate his effort to investigate this and his cause is probably spot on, but  I think his recommendation, beyond changing the clamp, is most likely  beyond what most people will be able to do on their own.  I also think there is probably a different coating that could be used.  I'm sure what he recommends is used by some to mitigate the problem, but that material is very expensive, difficult to work with and toxic.  

I agree with you that just putting on a second spring clamp or a second worm clamp probably will have a big impact.  If corrosion has already started...it's probably too late.

Until we see some actual long term testing, it's really hard to say if it will help (IMO)

I plan to keep my fluid change every two years and maybe put a second set of clamps as you suggest.


R/

pak

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.

fstop32

I agree with @Yoshi_TAB and also appreciate Marks effort to dig into this problem.  Unfortunately, while I think he has a good solution to the problem, it's probably only going to be used by the DIY'ers.  I doubt Alde or nuCamp will take the time to change their production process.

I'll admit to a little bias as I did a lot of part-time auto mechanic work going through college and we were always using the worm clamps and I became very comfortable with them.  The spring clamps do offer speed in a manufacturing process plus they nullify the possibility of too loose or too tight for the installer.  I've never noticed a worm clamp loosening (not saying they don't) but I have seen the hose shrinking issue @Yoshi_TAB mentioned and that would require hands on to tighten so probably score one for the spring clamp there.  On the flip side I've never been hit in the head by a worm clamp flying off my pliers! 

When I rebuilt mine I went with 2 clamps at each connection.  I'm not comfortable with only having the hose pushed on the pipe 1/2" to 3/4".  I pushed my hoses on probably 1-1/4", used spring clamps toward the cut end of the hose and the worm clamp where the end of the pipe would be.  I also used some formed elbows so I never had a situation where a hose was bent coming to a connection.

I took @BrianZ idea of 1" heat shrink tubing to cover the aluminum stub on the convector pipe and then slid the hose over that.  When I change my Rhomar this fall and I'll be pulling one of those connections apart to see how the heat shrink is holding up...news at 11.

On the new convectors I bought each one had tool marks dented into the aluminum tubing at one end.  I also had those same dents on my existing convectors as well.  I shortened the stubs on the new convectors and repurposed my old convectors by shortening them appropriately.  I suspect the dents are from the process in the factory where they grip the pipe and then cut it, the griping part leaves small dents on the tube.

pthomas745

Here is Mark's part 2.  To quote William Goldman, concerning Hollywood:  "Nobody knows nothing."  We are all making educated guesses, and our "education" is getting better.  Until a lawyer pries open Alde, we just don't "know".

https://www.youtube.com/watch?v=z3pnhM3jqSA

Alde parts: I've been looking to replace my Alde gas valve. You can bumble around with Alde and their lack of service in the US, or...go to some of the European caravan webpages that have every possible spare part: convectors, etc.  Your mileage may vary, but the people I discussed my valve with from the vendor in England said it is a simple Alde part.  I would be a bit more careful about the pipes and fittings, however.

https://www.leisureshopdirect.com/gas/caravan-gas-water-heater/alde-water-heaters

tybladesmith

Here is the Alde pipe and convector sealing compound from their catalog.
Sealing compound | Alde (open link in another window by right clicking mouse)
This product was mentioned in the 3010-installation manual but not the 3020HE.
Loctite MR5923

Yoshi_TAB

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..

tybladesmith

@Yoshi_TAB, thanks for corroborating my research and questions from 2019.

BrianZ

@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

Yoshi_TAB

Hi, 

Wow, until I read many (not all) of the posts referenced above, I did not realize how long this has been  discussed.  I see that many of you have been trying to address this issue for a few years.  I very much appeciate your work on this.  For me, as a relatively new owner of a little over 2 years, it makes me nervous that a problem may be lurking out there and can appear "anytime" , possibly at the worst time while on a trip.

So how we can best come to  a concensus  of what  to summerize and  recommend  for the type of glycol you have (or maybe by  model year of TAB)? 

-Double clamp
-Double clamp with some type of sealant/coating on connectors
-Heat shrink
-Just routine fluid changes
-Inspect every 2 years, (or some time interval)
-etc.
-Combination of the  above

I realize there may not be a single or an exact answer since obtaining data has not been easy of when or  under what conditions  (fluid changed  or not) of when  corrosion is observed.

I see 3 categories of TABs (maybe there are more).  Is there different recommedations for each of them?  Or is it the same?

-A  TAB, delivered with the Rhomar (blue/Green) fluid?

-A TAB with the Century (yellow) fluid and have conducted routine fluid changes.

-A TAB with the Century (yellow) fluid but have not conducted routine fluid changes.

Can we set up a "team" of folks to create a set of consice recommendations of what we know today.  I realize it may change based on addtional observations or data.    Maybe you have and I didn't see it yet in the many previous posts, but is there a chance NuCamp would help?

Also, I read in a few posts that some of you reached out to Alde and or NuCamp on this issue, but I never saw (or got to yet) if  a responce was received.  

Thank you,