Corrosion of Alde Convectors

ScottG

@pthomas745, @BrianZ did post a followup to the heat shrink issue in October, but it was in a different discussion. Not sure if you caught this latest installment.

pthomas745

The one about the adhesive?  Yes, I did.  I finally got the glycol out, and the stubs exposed.  Do have corrosion, but no real "pitting".  Things cleaned up reasonably well.  I'll have pictures later in the weekend. 

pthomas745

And, a few pictures of my corrosion cleaning experience.  I found nothing that hasn't been encountered here in the numerous (and incredibly valuable) sources posted before. 

What did strike me was how some of the hoses were tortured onto the ends of the convectors.  This is the passenger side convector.  It seemed to be actually bent and pushed onto the stub.  Everything worked against the hose: the little window the hose runs through from the rear convector locks it in a strange orientation, and the last few inches of hose has to be "pressed" onto the stub.   I intend to widen the little "window" back there for more hose room.  I'm going to put some spacers with longer screws to simply move the convector off the wall just a small quarter of an inch to allow the hose to take a straight shot onto the stub. 

This is the rear convector, driver's side.  The stub end going into the Alde tank was completely clean, just marked from the hose, maybe?  The hose out from the Alde check valve needed cleaning.  This was another hose that was manipulated to reach the proper position on the stub.  This one may be lifted just a bit to relieve the pressure on the hose. On the  passenger side of the rear convector, both stubs had the "ordinary" corrosion.

The Alde check/non return valve was corroded at both ends.  The side closest to the air bleeder valve had more corrosion, which made it difficult to remove.  (More on this in the "Changing out the Alde Glycol thread.)  I had cleaned the other stubs with scrubby pads, a bit of vinegar and baking soda, and finally a few strokes with a Dremel wire brush.  I wound up with the valve over by the kitchen sink, and realized Barkeeper's Friend is my go to aluminum cookie sheet cleaner.  It made very short work of the corrosion after slathering on a paste.  The pic below was just the BKF and a scrubby pad.  I used a minute with the wire brush to smooth things down.  My other stubs looked like the check valve after cleaning.  You can see the "wearing" on the aluminum, but none of mine were close to breaking completely through the structure.

There still seem to be more bulging spots in some connections.  The ones I can easily get to are the two hoses coming out of the expansion tank.  There are hose clamps there, but I'm not exactly sure what they are holding together.  Simple aluminum connectors?

I did not expect the corrosion in some spots to be so "goopy".  I know it probably meant that glycol had sat there for some time still in a liquid state, and the "goop" would eventually turn into the hard knobs that had to be ground off.  There was conversation in this thread about the Loctite and Permatex Gasket Sealant.  Is this "goop" and flaking we have seen in the past results of the gasket sealant deteriorating?  The sealant mixes with the glycol and turns into this paste?

And, last:  there have been some FB posts discussing some owners experiences with the corrosion cleaning.  One thread I looked at the other day has a comment about the hoses themselves.  Mark Turney pointed out they are simply ordinary EPDM heater hoses.  Maybe I remember one owner changed out a hose.  I wonder if the "forced" hoses, if replaced with something with more flexibility,  would be a good solution for a proper installation.

I will button this all back up in a few days with conformal coating and extra hose clamps.  I'm on the fence about the silicone shrink wrap so far.

I'm taking a Tab Yoga Merit Badge for this activity.  And I want to thank all the owners out there who contributed to this thread who gave me the confidence to do this work. 

DanSees

Pthomas745 On a recent trip to Pittsburgh PA over the Christmas holiday. I developed a leak at the check valve you show in the picture above. My hose wasn't swelled but there was corrosion on the AL & where the rings are my AL tube was cracked. I thought the rings were crushed into the corroded AL due to the pressure of the clamps. But now i know the rings are where they crimped in the check valve to keep it in one place. Not sure how I can do this to the copper tube I used. I was able to use a copper tube and put the plastic sheck valve in the copper tube. However It doesn't fit snug. I made it back home but haven't had time to look deeper into this. I suspect I have more corrosion in the system. 

pthomas745

@DanSees The check valves are pretty standard parts for all of the Aldes.  If you just need the tube the valve is set into, that is a bit over my head.  If you could find a way to crimp the proper sized "tube", it would seem that would be an easy fix.  There are several conversations about the size of the "tubes" used as connectors in the Alde if you look through this thread.  22MM seems to be the magic number.  This is one suggestion from "BrianZ" here in this thread who did a lot of work examining his convectors and cleaning things up.

https://www.amazon.com/dp/B01GQVDCOC

Whether or not that tube will hold the check valve, I have no idea.

When you examine your hoses and the connections at the convectors, you need to look closely for the tell-tale bulges where the hose clamps are.  You can ramble through this thread and see the many variations on the same theme.  Some connectors were completely corroded through.  There are ways to fix even the worst of the corroded ends.  I had "bulging" that looked as rough as many others, but the corrosion underneath was "not terrible" and I was able to clean them.  ( I have one left, so knock wood!)  And, even with my "limited" skill set, I was still able to get through this process, so far.  Getting the hose clamps loose has been the most difficult part of the process.

You might also try getting a check valve through the NuCamp parts process.  Drop Missouri Teardrops an email with a picture of the check valve and ask if one is available.

https://www.missouriteardroptrailers.com/

DanSees

Thank you for this information pthomas745. Are you the narrator Paul Thomas on the Facebook nucamp owners group? If so you always have very good information & replies. 

pthomas745

@DanSees yes, you have blown my cover!  The only reason I have any information at all is from the phenomenal user group here at the Forum.  This group, and other FB commenters, deserve every bit of the credit.  Like your aircraft mechanic skills, there is a massive amount of talented people here.  Me?  I learned how to use a hose clamp tool recently!  My only real skill is Google search.

pthomas745

Update: corrosion cleaned, ready to start putting things back together.  Thanks again for all the good advice.  With the proper tools I managed to heat shrink the convector ends. For those of you trying the conformal coating, please take the warnings seriously about fumes, etc.  Stuff is..harsh.  I wound up with my N95 masks on, used fans to keep the fumes away, etc.  But it went on very easily. 

While examining the convector ends, the non return valve, and that small "stub" that connects the hoses into the expansion tank:  I was getting quite close to having the corrosion eat all the way through the aluminum.  On the inside of the return valve and the "stub", there were small "eruptions" on the inside of the tubes.  I left these alone.  But: I would much prefer to replace the two parts. Especially that "stub" on the rear convectors that are hidden from sight.  Of all the places for a failure, that would be the worst.

What I learned while reading and re-reading all these posts is: the sizes of the hoses, and the sizes of each of these little "stubs".  Alde does have a part number for the stub: 1900-119, which is a simple 70mm long, 22mm aluminum tube.  In the English "caravan" parts places, it sells for a couple of dollars, but with a huge shipping cost.  Is it possible to replace that simple stub with a 22mm aluminum pipe like the one linked below? I bought two of these, and they fit the diameter fine, but they would have to be cut down a bit. I don't know enough about "anodizing" and whether or how the interior of these pipes would handle the Alde glycol

https://www.amazon.com/dp/B09FNS6C6F?ref=ppx_yo2ov_dt_b_product_details&th=1

I would still prefer to have a non-compromised connector at that point.

I also will modify the hoses going into the expansion tank.  I purchased a "3 inch, 90 degree" elbow that drops down an extra inch from the tank, and extends an extra inch to the rear convector.  The EPDM heater hose is easy to cut and size. This will mostly eliminate the difficult angles in that connection.   I'm just a bit concerned with that "stub".

DanWeitzel

pthomas745 said:

Update: corrosion cleaned, ready to start putting things back together.  Thanks again for all the good advice.  With the proper tools I managed to heat shrink the convector ends. For those of you trying the conformal coating, please take the warnings seriously about fumes, etc.  Stuff is..harsh.  I wound up with my N95 masks on, used fans to keep the fumes away, etc.  But it went on very easily. 

While examining the convector ends, the non return valve, and that small "stub" that connects the hoses into the expansion tank:  I was getting quite close to having the corrosion eat all the way through the aluminum.  On the inside of the return valve and the "stub", there were small "eruptions" on the inside of the tubes.  I left these alone.  But: I would much prefer to replace the two parts. Especially that "stub" on the rear convectors that are hidden from sight.  Of all the places for a failure, that would be the worst.

What I learned while reading and re-reading all these posts is: the sizes of the hoses, and the sizes of each of these little "stubs".  Alde does have a part number for the stub: 1900-119, which is a simple 70mm long, 22mm aluminum tube.  In the English "caravan" parts places, it sells for a couple of dollars, but with a huge shipping cost.  Is it possible to replace that simple stub with a 22mm aluminum pipe like the one linked below? I bought two of these, and they fit the diameter fine, but they would have to be cut down a bit. I don't know enough about "anodizing" and whether or how the interior of these pipes would handle the Alde glycol

https://www.amazon.com/dp/B09FNS6C6F?ref=ppx_yo2ov_dt_b_product_details&th=1

I would still prefer to have a non-compromised connector at that point.

I also will modify the hoses going into the expansion tank.  I purchased a "3 inch, 90 degree" elbow that drops down an extra inch from the tank, and extends an extra inch to the rear convector.  The EPDM heater hose is easy to cut and size. This will mostly eliminate the difficult angles in that connection.   I'm just a bit concerned with that "stub".

Alde has those little stubs in plastic.  I bought some spare parts from another T@B owner and those plastic stubs were included.  I believe you can find the part number on the Alde USA website.  All my stubs were corroded so I replaced them with the plastic ones. 

pthomas745

Thanks, Dan.  I sometimes wonder how many other smaller engineering decisions were made on the US Aldes delivered after the "Magic Glycol Change" date.  How are the convectors different?  The hose configurations and install processes?  The little metal "stubs" that we see corroded?

Do you know what year trailer/Alde the plastic stubs came from?

Did you try reaching out to Missouri Teardrops? I sent an email this morning with the parts descriptions but have not heard back yet.

DanWeitzel

pthomas745 said:

Thanks, Dan.  I sometimes wonder how many other smaller engineering decisions were made on the US Aldes delivered after the "Magic Glycol Change" date.  How are the convectors different?  The hose configurations and install processes?  The little metal "stubs" that we see corroded?

Do you know what year trailer/Alde the plastic stubs came from?

Did you try reaching out to Missouri Teardrops? I sent an email this morning with the parts descriptions but have not heard back yet.

The guy I bought the spare Alde stuff from received the parts under warranty so I'm thinking it was a 2020 or 21 but not sure.  Here's a pic of my old stubs which were replaced with the plastic ones.

mtns4me

I just wanted to thank you all for this thread and all the pioneers that did this before me so I could see that I could do it myself. I have a 2015 320 Q layout Outback and over New Year weekend camping, we had a glycol leak in the middle of the night and didn't realize that it was all over the floor and the pup was covered in it. We took the pup to emergency clinic to make sure all was well, which she was thankfully, and then I found where the corrosion had gotten so bad that it cracked the tube at the connection. I trimmed off, cleaned and re-attached, added glycol so we could continue camping. Last day, found another leak in the back from another cracked tube at the connection due to bulging corrosion. Once home, I found this thread, contacted Truma to get parts and replaced all tubes, connections, trimmed ends of corroded convectors, painted ends with Miracle Paint (thank you Sequimite and others for recommending), and added a passenger side drain (thanks to YouTube channel "Tab Trailer Upgrades and Maintenance").  I have now put everything back together and working great! I did go back with the old transfer fluid since no exposed aluminum now, with the exception of the auto bleed valve at the unit (which I also replaced), and I plan to change the glycol every year or two, which will now be easier since I now have a low point drain on each side. Thank you all again for the posts! Now need to learn to pull the refrigerator so I can replace that propane hose that has rubbed. Will look for posts, but if anyone has any tips or suggestions please message me.

pthomas745

@mtns4me Welcome to the Forums and what nice work!

I'm curious about how the "Magic Paint" worked for you, as far as handling it, odors, etc.  Those were Mark Turney YouTube videos about the extra drain and the "Magic Paint".

You say you worked with Truma for parts?  Other members haven't seemed to have much luck on that score.

On your last photo, the two connectors on both side of your drain valve are:part of the drain valve assembly itself?  Or, are they the "newer" plastic stubs? 

I managed to order a spare non-return valve and a few of the "stubs" through Missouri Teardrops and NuCamp.  I was told they were shipping plastic ones but they would fit, and now I'm a bit curious.

mtns4me

@pthomas745 Thanks! The Paint I got was called "Miracle Paint" from:

https://mercedessource.com/store/miracle-paint-permanent-rust-repair-pint-black-free-brushes-and-gloves

It came with lots of disclaimers but very easy to apply and use. Hopefully this will protect the convector ends from future corrosion as anticipated, but this site above and their YouTube videos looks like that is what it is for. Time will tell, for sure!

Mark Turney's videos were extremely helpful!

Not sure how, but I got lucky with Truma and ordered replacements for everything except I reused my convectors. Almost every one of my connections were bulging with corrosion, so I felt better replacing and not trying to cut hoses and/or reusing "stubs". 

I got an extra drain value and bought a handful of the "stubs" which were all changed to plastic. The two ends of the drain in the picture in my post you can see where I added the new plastic stubs.

pthomas745

My order of the "stubs" and another non-return valve arrived yesterday.  This is what the plastic stubs look like.

An owner of a 2014 on the FB page went to school with this thread and cleaned his convectors, etc also.  They reported that they were able to order the parts needed with a direct call to Truma/Alde.  I'm not sure if there has been some change in policy/ideas from Alde, but maybe, just maybe, they will be a bit more helpful with the parts side of the Alde.

This phone number for Alde: 855-558-7862

DanSees

How about the non-return check valve is it still alluminum? I replaced mine with a copper tube with the plastic check valve I cut out of the corroded alluminum tube. Can I ask how much the non-return valve cost? 

pthomas745

Yes, the non return valve is still an aluminum part.  There is a 60 mm version and a 90 mm version.  They sent me the 90 mm version, that will still work, probably.

The total for 6 of the plastic "stubs" and the valve was 46 dollars with shipping, etc. The packing slip did not break down the cost per item.  Took three days for shipping from Ohio, so I'm guessing the shipping cost may have been 1/4 of that 46 dollar total.  And, I hope Missouri Teardrops got compensated a bit, too. I have no complaints about this: I didn't think I'd be able to order any Alde parts, and it was nice to get them to Socal in three days or so.

Looking again at the FB post, that owner says that Alde charged 1.41for each stub.  So...I think working through Alde would be a better deal.

DanSees

pthomas745 said:

Yes, the non return valve is still an aluminum part.  There is a 60 mm version and a 90 mm version.  They sent me the 90 mm version, that will still work, probably.

The total for 6 of the plastic "stubs" and the valve was 46 dollars with shipping, etc. The packing slip did not break down the cost per item.  Took three days for shipping from Ohio, so I'm guessing the shipping cost may have been 1/4 of that 46 dollar total.  And, I hope Missouri Teardrops got compensated a bit, too. I have no complaints about this: I didn't think I'd be able to order any Alde parts, and it was nice to get them to Socal in three days or so.

Looking again at the FB post, that owner says that Alde charged 1.41for each stub.  So...I think working through Alde would be a better deal.

I agree $46 does'nt seem bad. Thanks for the breakdown. 

Martine

Lots of good info in this thread! I had my own issues with corrosion in a 2019 320 S that we fixed, with factory-supplied convectors from NuCamp. After that, we had no problem. 
I just sold that 320 and yes, did disclose what had happened and what we did. What I'm wondering is if this is also common in 400s?? I've been searchign threads and can't find mention of it in the 400s. Thanks for any help with this!

ScottG

Good observation, @Martine. When this discussion first arose three years ago, I assumed age and use was a factor, and since the oldest T@Bs were all "320s" it made sense that's where where most of the problems occurred. Although the exact causes(s) remained elusive, by now I would expect to hear reports of this corrosion surfacing in 400s.

Both nuCamp and Alde remained oddly silent amid mounting concern over this issue, and in recent times discussion of it has subsided considerably. Perhaps there was some quiet change in the construction or assembly of newer models (my guess would be better sealing of the rubber heater hoses to the aluminum convector stubs). Maybe the convector stubs in 400s are harder to get at, or perhaps 400 owners just aren't as interested in looking at them. Beats me. I'm curious to see if any 400 owners come out of the woodwork after your post.

rh5555

@ScottG: go visit https://tab-rv.vanillacommunity.com/discussion/comment/196574.  That's where the TAB400 discussion is.

ScottG

Ah, right! Just last month--no wonder I couldn't remember it!  :-)

I'm their leader, which way did they go?

pthomas745

When I see the "newer" 400's and the convectors and hose fittings at the end of the convectors, I seem to think the "attention to detail" is much greater on the hose fittings, the clamping, the angles the hoses connect to the convector ends, etc.   I would really like to examine any newer trailer with particular attention paid to those sorts of items.  The photo in the RH5555 thread above shows what I'm talking about: the convector/hose connection circled seems to be quite precise, with that 90 degree bend at the exact spot to allow a straight shot to the convector end.

For my 2017, I found all the evidence that the hose connections installed were considered fine "as long as it didn't leak", with no thought given to the strange hose angles meeting the convector.  I would be willing to bet that my trailer started to corrode when the glycol filled the gaps on the hoses the very first time the Alde was run.

grassgd

Like many Tab owners, I experienced the corrosion of the Adle convectors and aluminum connectors used in my Tab 320s.  The corrosion on mine and other owners always seems to concentrate under the rubber hoses that are attached to the aluminum convectors or aluminum pipe/connectors used in the system. 

The solutions everyone seem to have tried concentrate on cleaning the convector ends or cutting off the corroded ends and applying some type of protection to prevent the glycol from contacting the aluminum under the rubber hoses. That’s what I did and I think that’s the proper thing to do. Whatever is used to coat or cover the ends of the convectors, the important thing is to use something that the glycol cannot get under.  In my case, I choose to glass bead the convector ends after cutting off the corroded ends and coating with a 2-part epoxy primer.

The other recommendation is to change over from the old Century antifreeze to the Rhomar antifreeze and ensure the antifreeze is changed every 2 years.  This preventative measure seems to rely on the new Rhomar antifreeze having a better corrosion inhibitor chemical package and routine fluid changes will ensure the inhibitor which degrades over time will be replaced.

In my case, there was no corrosion of the aluminum convectors or connectors on the inside which leads me to believe the corrosion inhibitor in the Century antifreeze was still effective even though it was 3 to 4 years old.  I am not making a plug for the Century antifreeze, but not sure that was the cause of the corrosion problem.

In digging on the internet looking for possible root causes of the corrosion experienced, I came across an article about closed loop cooling systems which may shed some light on the root cause in our Adle system. The article is titled “Monitoring and Treatment of Closed-Loop Cooling Systems” posted on www.powermag.com.  

The excerpt is:   “In a closed-loop system, oxygen pitting is the most common type of corrosion ………. In order for oxygen pitting to occur, there must first be a deposit that covers a portion of the metal surface, creating a differential between the oxygen content underneath the deposit and the oxygen content in the bulk water. The oxygen-deficient area underneath the deposit becomes the anode, and the area around the deposit that is exposed to the bulk water becomes the cathode. This big cathode, little anode configuration causes concentrated and accelerated pitting in a confined area, producing pinhole leaks.”

In our system the “deposit that covers a portion of the metal surface” is the rubber hose which creates a craves filled with glycol which may become oxygen deprived/isolated from the glycol flowing through the system which has oxygen in it since we have an open system.  This becomes the anode causing concentrated and accelerated pitting in this confined area. Sound like what we are seeing.

In closing, the solution to isolate the aluminum under the hose connection should resolve the problem as long as the material used stays bonded to the aluminum.  The other option might be to eliminate oxygen from the entire system, but that would be more difficult……just a thought at this point.

fstop32

I "borrowed" @BrianZ heat shrink idea (uh, check is in the mail Brian...) and I later did notice a slippery situation which I suspect can be attributed to the adhesive on the inside of the heat shrink getting "gooey" as the glycol heats up and was allowing it to slide and shift a little.  I used 90 degree elbows and lots of hose supports in my rebuild to prevent any unwanted tension, compression or movement and I double clamped all the connections so I've not experienced any leaks or separated connections so far.

ScottG

I've always been skeptical that the Century glycol--or even the failure to change it at recommended intervals--was the root cause of the convector corrosion issue. The idea of "crevice corrosion" was floated early on in this discussion. Detailed explanations like those provided by @grassgd and the guy who does the T@B videos on YouTube--not to mention the lack of corrosion inside the convector tubes--further support this hypothesis.

bergger

While I don't understand all the science behind this, I always figured something was going on with glycol trapped between the rubber hose and the aluminum convector stub that caused the corrosion.  However in reading all this I still don't understand why some systems have corrosion and others do not.  Some are years old and fine and others are newer and have major issues.  I can only hope that the new Rhomar that I switched over to will help and hopefully the new plastic stubs Alde is using will completely prevent the issue going forward.  If I end up having problems I guess I'll switch over to the plastic stubs.  Although I still don't understand how one goes about replacing the aluminum stubs with plastic ones. 

DanWeitzel

bergger said:

While I don't understand all the science behind this, I always figured something was going on with glycol trapped between the rubber hose and the aluminum convector stub that caused the corrosion.  However in reading all this I still don't understand why some systems have corrosion and others do not.  Some are years old and fine and others are newer and have major issues.  I can only hope that the new Rhomar that I switched over to will help and hopefully the new plastic stubs Alde is using will completely prevent the issue going forward.  If I end up having problems I guess I'll switch over to the plastic stubs.  Although I still don't understand how one goes about replacing the aluminum stubs with plastic ones. 

The plastic stubs are only the straight thru connector that connect two pieces of rubber hose together.  They do not attach to the convectors or replace the convector ends, these remain aluminum.  

bergger

Ahh...that makes sense.  So the only way to protect the convectors if you have corrosion is to coat the stubs with a protectant. Hopefully ours remains corrosion free.  If not maybe I'll just remove the Alde and replace it with a Truma Combi unit.  I kinda wish NuCamp would go that route in the future.  

grassgd

bergger said:

While I don't understand all the science behind this, I always figured something was going on with glycol trapped between the rubber hose and the aluminum convector stub that caused the corrosion.  However in reading all this I still don't understand why some systems have corrosion and others do not.  Some are years old and fine and others are newer and have major issues.  I can only hope that the new Rhomar that I switched over to will help and hopefully the new plastic stubs Alde is using will completely prevent the issue going forward.  If I end up having problems I guess I'll switch over to the plastic stubs.  Although I still don't understand how one goes about replacing the aluminum stubs with plastic ones. 

It is puzzling why some don't have this problem and others do. 

Even if some aluminum components are anodized better than others, I assume that would not stop the crevice or anode/cathode corrosion I described earlier. 

If nuCamp was using something on the convector ends and connectors during assembly (I recall others talking about a Loctite product or something), perhaps that product could effectively fill the gap between the aluminum and the rubber to prevent glycol from entering and prevent the anode/cathode from setting up.  Perhaps during installation some installers applied a heaver or better coating on the ends that do not corrode.