Corrosion of Alde Convectors

fstop32 · April 2021

Wanted to drop this pic since there has been comments on "white flakes" showing up in glycol samples. These flakes were on the inside of some of my rubber heater hoses (in this case the short hose connecting the pump to the input on the boiler). I don't know if that's normal or another sign of something going on that shouldn't...just wanted to share.

ChanW · April 2021

Yep, checked ours and we have a bit of bulging in the hoses, not too extreme, and only on the convectors' lower connections.

Also, it seems to be only on the one side of the hose clamps, the 'liquid side', so to speak.

I wonder if it's necessary to remove and clean up the parts, especially in this case of a minor bulge, or if only thoroughly changing the glycol more regularly would be enough to stop it from getting worse.

Tampakayaker · April 2021

fstop32 said:

Wanted to drop this pic since there has been comments on "white flakes" showing up in glycol samples. These flakes were on the inside of some of my rubber heater hoses (in this case the short hose connecting the pump to the input on the boiler). I don't know if that's normal or another sign of something going on that shouldn't...just wanted to share.

Looks like grated coconut

ScottG · April 2021

FWIW, my plan is to fully drain the system, flush it several times with distilled water, then refill with fresh glycol. I may even get to this this weekend.

I'm going to try to drain the convector loop by removing the short hose between the upper and lower convectors under the passenger bench. Neither of those have bulges.

I'm hesitant to to try and remove hoses where there are bulges. I'm not sure what could be done to clean up or mitigate corrosion that has already started, and I'm afraid too heavy a hand may damage the convectors in those locations. I think I will just keep on keepin' on until the condition gets critical or until an actual leak develops (as was the case with @fstop32).

Denny16 · April 2021

Scott, you should be ok to remove and inspect the connections thst have a little bludgeoned. You can also clean any depots from the tube and hose, which I would remove and flush out with water,to get rid,of any accumulated deposits. Just be gentle and proceed slowly.
cheers

fstop32 · April 2021

FWIW... @ScottG, I think you will be fine on connections not showing a bulge. At some point if corrosion exists AND has pitted the fitting enough then taking it apart and cleaning MIGHT cause a slow leak because the surface of the pipe is rough enough that the hose & clamp cannot properly seal it off. Personal preference here but I prefer the US style clamp that has the screw for adjustment over the spring clamps (prolly just because that's what I cut my teeth on growing up).
I wonder if anyone makes a "sealant" that works with aluminum that would help seal up that rubber to pipe connection when you put them back together?
@ScottG I would plan to keep a close eye on the worst bulges over time. It looked like the result of the increasing bulge was pinching the rubber hose back against the spring clamp and sprung the leak there. When mine started a slow leak I didn't notice it until it had run onto the floor and then wicked under and up into the plywood bench panel and shower wall. What caught my I first was the discoloration and "wet" look. I'll be replacing that panel plus a few others in my rebuild.

Tampakayaker · April 2021

I'm guessing spring type clamps on an assembly line are quicker and more consistent quality.

If they used the screw type, one person might overtighten and damage the pipe and the next person might not tighten enough causing a leak.

Denny16 · April 2021

@fstop32 3M 4200 or similar marine sealant would work well, lightly applied, so not to get any inside the tube, should work. We used this to isolate and seal fittings to aluminum masts to prevent corrosion, including stainless fittings. If you go with the screw type hose clamps, get the correct size, and use marine grade stainless clamps.
cheers

Ratkity · April 2021

@fstop32 Rescue Tape! That stuff is magic. Forget anything like Flex seal. I used this stuff to seal my wheel wells from water intrusion (an issue with the Retro, not the T@B).

I do keep Flex Seal tape in the camper to cover places where I see some of the silicone seals parting when I'm out camping. Don't you always see the issues while out on the road?? I think the trick to using Flex Seal on minor things is to squish the edges to prevent dirt and water from getting under the tape until a permanent fix can be done later (Omgosh, a Flex Seal lesson! Monster WaterProof tape is the same, btw).

fstop32 · April 2021

Good points on the clamps @Tampakayaker and @Denny16...spring clamps would definitely be faster on the assembly line! Besides if I go back with spring clamps then I'll have to buy the pliers! That's why guys like me have hobbies, so we can buy tools!

I love Rescue Tape!

pak · April 2021

After several cups of coffee staring at the problem, I have come to the conclusion this will not be an easy fix for me. My cs-s reservoir is behind the front wall in the bathroom. The access panel is way too small for me to get to the hoses. I can make the access larger as one clever fellow has done and posted here or I can look into changing the fluid by breaking the hose fittings. Durning the next interval change I will research and source some fittings the will improve access. I at this time have no evidence of corrosion but I am of the opinion it is caused by the interaction with the aluminum exchangers. They appear to be constructed of bare metal without any additional corrosion barrier other than the natural surface oxidation, which is minimal. I also will look into better constructed exchangers, perhaps even copper. The puzzle is still in play. This forum has been terrific. Thanks to all.

ScottG · April 2021

@pak, copper doesn't play well with aluminum--copper convectors may well encourage corrosion of the aluminum boiler.

I finally tackled my glycol change today, complete with a more-thorough-than-planned inspection and flushing of the system prompted by this recently discovered corrosion issue. In short, the news is good. I will post details and photos tomorrow.

Denny16 · April 2021

Copper is a poor choice for a heating system, whilst it is a better heat conductor than stainless, aluminum is better yet. Also copper corrodes more readily than aluminum, and as previously mentioned does not play well with other metals in the system especially the aluminum used in the boiler.

I just finished replacing a copper pipe manifold on my well pump system. The mineral in the well water had corroded a hole in one of the copper pipe connectors. I ended up replacing the entire main pipe manifold system to schedule 80 PVC, no more corrosion issue.
cheers

fstop32 · April 2021

Ditto @ScottG and @Denny16 about mixing copper and aluminum. Glad to hear you say "good news" @ScottG!

ScottG · April 2021

Yesterday I decided to tackle changing my long-neglected glycol. Although I originally anticipated this to be a relatively straightforward procedure, the recent concerns about corrosion of the aluminum fittings prompted me to do a little inspection in advance of the actual fluid replacement.

I started by disconnecting a few hoses. When that didn't cause the system to turn to dust in my hands, I got a little bolder and kept going. Eventually I removed the hoses from every location at which they were clamped to an aluminum fitting. Here is what I found...

First, the connectors at the Alde itself were pristine, and--as far as I could peer down into them (not very)--there was no evidence of any corrosion or other damage extending into the boiler.

However, every fitting in the convector loop had some degree of greenish salt-like deposits between the rubber hose and the outside of the fitting, and these deposits were associated with corrosion on the outside of the fitting. Some fittings were worse than others--in places where the build-up was greater, it had started to distend the hose, resulting in those characteristic bulges discussed previously.

The good news was that in all cases the corrosion was superficial. The fittings were still solid and the inner surfaces remained clean and undamaged. Here are photos showing the outside and inside of the aluminum connector just downstream of the automatic air bleeder:

Image: https://us.v-cdn.net/5021717/uploads/editor/ur/ktlwk8sxxicm.jpg

Image: https://us.v-cdn.net/5021717/uploads/editor/o6/10dw6qgn6c6j.jpg

In most cases, the hoses themselves had crystals stuck loosely inside them. Since most of them were disconnected at this point anyway, I took them inside for a good scrubbing out with a soft toothbrush and a thorough rinse with hot water. Here's a typical example:

Image: https://us.v-cdn.net/5021717/uploads/editor/wk/kc8ojg4csb5t.jpg

Before reassembling, I cleaned up the affected aluminum with hot water and a scrubby pad. This removed the bulk of the crystalline deposits on the outside of the fittings. Here are before and after pics of the convector under the passenger-side bench:

Reassembly was easy enough, and no leaks were evident after refilling the system. However, if you attempt this I strongly suggest noting which hose goes where. Careful attention to this detail will result in you only having to reassemble the system once. ;-)

If you are interested in reading about the actual glycol replacement, I've posted the details of that job here.

ChanW · April 2021

@ScottG, thanks for giving me hope here...
Did you apply any kind of sealant or other goop on the aluminum before you replaced the hoses, or are you simply counting on the anti-corrosion properties of the glycol?
Did you use a pump for flushing & refilling the glycol?

pak · April 2021

No copper, got it. Thanks for the shout out.

ScottG · April 2021

@ChanW, I didn't treat the aluminum in any way. I wasn't sure how much difference it would make with the corrosion already underway, and given the slow pace of deterioration figured it wasn't critical and that I would just keep an eye on thongs going forward.

As planned I used a hand pump for flushing and filling. The filling is documented here.

I also flushed the system several times with distilled water. Since I had everything apart, I flushed the convector loop and the boiler separately, but you could also do in the same manner as I describe the filling.

ChanW · April 2021

I saw your write-up in the other thread @ScottG. Nice work.

Thanks for being the guinea pig, er, point-man!

Denny16 · April 2021

Giving the corrosion on the outside of the aluminum connectors some thought, it may be caused by the old glycol sitting in constant contact. The little but that gets in between the pipe and the hose, is stagnant, not circulating in and out, it gets pushed in there and while the Alde is in use, it stays there. So no flushing action of circulating glycol as inside the pipes and hoses.

ChanW · April 2021

Makes sense @Denny16.

I wonder if the hose clamp should be fitted farther away from the convector body, or maybe a second clamp. Less metal with this sort of contact.

Or is there some kind of glycol-resistant sealant or anti-corrosion compound that could be applied to the pipe-stub before assembly?

Denny16 · April 2021

The pipe stub could be anodized. Double clamping is a good idea, if not just to seal more of the connection, it also will add additional security from coming undone. All boat fittings connect to bilgemoump systems or below the water fittings are all double clamped. I did this with my water hose connections on my water well system.
cheers

fstop32 · April 2021

I reviewed the locations of the bulges and it was a mixed bag...some on the input side and some on the output side. Since the spring clamps have to go on during assembly I'll have an advantage of being able to double clamp everything (that's the glass half full way of looking at it).
In an Alde parts catalog they had Loctite 5923 listed and said it's good for threaded and rubber to metal connections. I pulled up the spec sheet but it didn't offer any comment when it comes to corrosion.

gulfarea · April 2021

My vote after hearing about pin hole leaks and very bad corrosion would be to buy SS heat exchangers for all the T@BS as I can see this is going to be an on going problem! Yes SS may not transfer heat as fast but I can wait for the heat and this corrosion problem is getting ridicules! I love the Alde over the loud gas hot air types so will stay with Alde. Art

ChanW · April 2021

Now I remember seeing that Loctite 5923 sealant in their catalog.

Perhaps that's the problem - it was not used with some of the connections when assembled, or not properly. The bulges on mine are random enough for it to be human error.

Looks like a good idea to use it now though..

fstop32 said:

I reviewed the locations of the bulges and it was a mixed bag...some on the input side and some on the output side. Since the spring clamps have to go on during assembly I'll have an advantage of being able to double clamp everything (that's the glass half full way of looking at it).
In an Alde parts catalog they had Loctite 5923 listed and said it's good for threaded and rubber to metal connections. I pulled up the spec sheet but it didn't offer any comment when it comes to corrosion.

Denny16 · April 2021

@gulfarea, good luck on finding stainless heat convectors thst would work with the Alde. If some are available, the cost would be much more $. Also, if properly maintained, and the glycol changed as required, you should not have this corrosion issue. Also periodic inspection of the hose connections is a good idea. Most of the trailers in this discussion with the corrosion issue, did not change the Alde glycol every two years, one went 5 years.

Cheers

gulfarea · April 2021

@Denny16 For 31 years I owned a Diesel garage. Worked on all kinds of gas and diesel radiators and heaters. If we had this problem and had to change antifreeze every year in our cars, I say something is wrong! Art

fstop32 · April 2021

@Denny16 and @gulfarea I think you both have good points. I have wondered myself why these boiler type systems need so much attention (or much better heat transfer fluid), you'd think someone would have made some significant improvements. But I also suspect these systems were as much designed to sell in their niche market but had to fit a budget point. Hence, the system doesn't cost an arm and a leg to purchase but the maintenance is much more involved.
@ChanW I plan on using the sealer on my new convector connections, I don't think it can hurt and it might just add the barrier between the pipes and the rubber to deter corrosion. I guess I can see them not using it during initial assembly because it's labor intensive, but since it's my labor this time I'm going for it.

And you never know what you'll find when you look close enough...I think I'll be adding a screen to the propane exhaust port for the boiler

ChanW · April 2021

Huh! And I heard it was mud-daubers that like to build their condos in propane exhaust pipes!

There's a good stainless steel screen cap discussed somewhere here. Works good.

Ah. Here (Amazon link):

tybladesmith · April 2021

Bug screens are a good idea! @ChanW I used the same screen.

Corrosion of Alde Convectors

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