Corrosion of Alde Convectors

grassgd · April 28

Finished repair and installation of the convectors which I repaired by cutting off the corroded ends and coating with 2 part epoxy.

I mechanically cleaned the inside of the convectors and EPDM hoses to remove the white coating shown below:

Image: https://us.v-cdn.net/5021717/uploads/editor/mo/viup3b8dzn6a.jpg

This picture shows the white power that came out:

Image: https://us.v-cdn.net/5021717/uploads/editor/ky/te7geys0a1dw.jpg

This shows a before and after cleaning of a convector:

Image: https://us.v-cdn.net/5021717/uploads/editor/9a/ztnckwrbss1i.jpg

I don't really know what the white coating removed was. Don't think it was any type of corrosion because it was also in all the EPDM hoses. My guess is was either a deposit of scale or a deposit resulting from the corrosion inhibitor in the original glycol.

I also trimmed some of the EPDM hoses where I was concerned with the integrity where there was excessive budging form the corrosion. I used some marine stainless steel railing to make connectors in lieu obtaining replacements form Alde since I had to accommodate for the shorter convectors and trimmed EPDM hoses.

Here is a picture of an example where I used a longer SS connector due to a shorter convector and trimmed EPDM hose:

Image: https://us.v-cdn.net/5021717/uploads/editor/c7/dysy4ewzhjgw.jpg

Another picture showing the SS connectors being used:

Image: https://us.v-cdn.net/5021717/uploads/editor/wb/zxrkn9bl34ll.jpg

I actually salvaged the original Alde check valve from the corroded aluminum pipe and installed it in a piece of stainless steel pipe.

manyman297 · April 30

I may have asked this before but have we heard of any corrosion happening on Rhomar-filled systems? I did a fluid exchange (Rhomar to Rhomar) last summer after two years and it looked practically new and no signs of crystallized chunks during the exchange.

pthomas745 · April 30

We have all been anxiously waiting for the answers to this question, but it might take several more years for to find out. Since the Alde Change thread and the corrosion threads were started, we learned so much about the glycol and how the Alde convectors and hoses were put together, etc. Was the glycol the cause of the corrosion? Or, was it the construction of the hoses and convectors with the insufficient clamping and sealing of the convector stubs?

Looking at the Alde construction of the newer trailers, it seems there are much better clamps, better hose connections (precisely measured hoses, etc).

On the other side: we have plenty of members with the older "Century" trailers who cleaned their corrosion, sealed the stubs in various ways, used better clamping methods/ideas, and stayed with the Century glycol. In a couple of years, we will have better answers about how those installation changes held up.

ReenieG · May 16

Looking through this updated thread again as I work on my Alde corrosion, I have a couple of questions for some of you. (I will create a new thread or add my total completed experience here when I get done)

@grassgd where did you get that brush? Is it a fish tank cleaner brush or ? if you have a name or a link that would be helpful. TIA

Has anyone replaced all of their hoses? I'm trying to find a good resource to do so, since IMO, while I'm doing a massive repair to the system anyway and want to avoid any leakage from something I may have not visually seen, it seems to me the whole system contains about 25ft or less of epdm hoses which may just be more prudent to start with new hoses and cut to length. Anyone? If so, please provide a link where you got your hoses from. That would be helpful. Also, there are a couple of elbows, one with the little metal thingy, not sure what it is called, so maybe that is salvageable or can be ordered as a part.

Also, it appears this metal T-pipe and brass screw on drain cock is another part that could be replaced for the glycol floor drain which is rubber with a plastic red drain plug. Is that a correct part for that and has anyone replaced theirs? Or do some of you already have that in place? I'm leery of using some of these older parts when in fact I have everything out of the trailer now and this would be the time to upgrade it. TIA

This hose available at Tractor Supply looks like it might work but I'm not sure about the specs on this. Anyone?

DanWeitzel · May 16

ReenieG said:

Looking through this updated thread again as I work on my Alde corrosion, I have a couple of questions for some of you. (I will create a new thread or add my total completed experience here when I get done)
@grassgd where did you get that brush? Is it a fish tank cleaner brush or ? if you have a name or a link that would be helpful. TIA
Has anyone replaced all of their hoses? I'm trying to find a good resource to do so, since IMO, while I'm doing a massive repair to the system anyway and want to avoid any leakage from something I may have not visually seen, it seems to me the whole system contains about 25ft or less of epdm hoses which may just be more prudent to start with new hoses and cut to length. Anyone? If so, please provide a link where you got your hoses from. That would be helpful. Also, there are a couple of elbows, one with the little metal thingy, not sure what it is called, so maybe that is salvageable or can be ordered as a part.
Also, it appears this metal T-pipe and brass screw on drain cock is another part that could be replaced for the glycol floor drain which is rubber with a plastic red drain plug. Is that a correct part for that and has anyone replaced theirs? Or do some of you already have that in place? I'm leery of using some of these older parts when in fact I have everything out of the trailer now and this would be the time to upgrade it. TIA
This hose available at Tractor Supply looks like it might work but I'm not sure about the specs on this. Anyone?

I'd be careful with the Tractor Supply hose, looks like its only rated for max 150 degrees. I believe the Alde runs hotter then that. All Alde parts are listed on this website: https://www.alde.us/

ReenieG · May 16

@DanWeitzel I saw that and that's why I questioned the specs on that hose, but... there are NO hoses on the Alde site. So I'm still in search mode.

DanWeitzel · May 16

ReenieG said:

@DanWeitzel I saw that and that's why I questioned the specs on that hose, but... there are NO hoses on the Alde site. So I'm still in search mode.

Here you go. https://www.alde.us/our-products/rubber-hose-1/?from-filters=22-mm,assembly-parts-rubber,heating-systems

grassgd · May 16

ReenieG said:

Looking through this updated thread again as I work on my Alde corrosion, I have a couple of questions for some of you. (I will create a new thread or add my total completed experience here when I get done)
@grassgd where did you get that brush? Is it a fish tank cleaner brush or ? if you have a name or a link that would be helpful. TIA
Has anyone replaced all of their hoses? I'm trying to find a good resource to do so, since IMO, while I'm doing a massive repair to the system anyway and want to avoid any leakage from something I may have not visually seen, it seems to me the whole system contains about 25ft or less of epdm hoses which may just be more prudent to start with new hoses and cut to length. Anyone? If so, please provide a link where you got your hoses from. That would be helpful. Also, there are a couple of elbows, one with the little metal thingy, not sure what it is called, so maybe that is salvageable or can be ordered as a part.
Also, it appears this metal T-pipe and brass screw on drain cock is another part that could be replaced for the glycol floor drain which is rubber with a plastic red drain plug. Is that a correct part for that and has anyone replaced theirs? Or do some of you already have that in place? I'm leery of using some of these older parts when in fact I have everything out of the trailer now and this would be the time to upgrade it. TIA
This hose available at Tractor Supply looks like it might work but I'm not sure about the specs on this. Anyone?

The brush used on the rubber hose cleaning was from Harbor Freight which was pulled through with a piece of rope. The brush used on the convectors is a 12 ga shotgun brush and associated rods for cleaning a shotgun barrel.

grassgd · May 21

ReenieG said:

Looking through this updated thread again as I work on my Alde corrosion, I have a couple of questions for some of you. (I will create a new thread or add my total completed experience here when I get done)
@grassgd where did you get that brush? Is it a fish tank cleaner brush or ? if you have a name or a link that would be helpful. TIA
Has anyone replaced all of their hoses? I'm trying to find a good resource to do so, since IMO, while I'm doing a massive repair to the system anyway and want to avoid any leakage from something I may have not visually seen, it seems to me the whole system contains about 25ft or less of epdm hoses which may just be more prudent to start with new hoses and cut to length. Anyone? If so, please provide a link where you got your hoses from. That would be helpful. Also, there are a couple of elbows, one with the little metal thingy, not sure what it is called, so maybe that is salvageable or can be ordered as a part.
Also, it appears this metal T-pipe and brass screw on drain cock is another part that could be replaced for the glycol floor drain which is rubber with a plastic red drain plug. Is that a correct part for that and has anyone replaced theirs? Or do some of you already have that in place? I'm leery of using some of these older parts when in fact I have everything out of the trailer now and this would be the time to upgrade it. TIA
This hose available at Tractor Supply looks like it might work but I'm not sure about the specs on this. Anyone?

I should have mentioned when using the wire shotgun brush to clean the convectors, I used a drill to rotate the brush while pushing it one way through the convector then dumped the white power out. I made a about four runs like that until the power out of the convector was turning grey instead of white which I believe was an indication of aluminum being removed and I stopped there. I then swabbed the convector with some lacquer thinner using a 12 gauge shotgun swab.

Freespirit · May 22

After 2 years of using the new Romario fluid this is what I have discovered so far. After draining the system I decided to inspect the reservoir tank. What I discovered is not what I expected. I will be inspecting all of the convector connections in the near future and hope to have better results. On this thread (page 14) you can read what I did to my system in late 2021 early 2022.

Horigan · May 22

Was this area clean before the Rhomar change, or could it be residual from the previous fluid?

Freespirit · May 22

This was a new tank provided by NUCAMP.

pthomas745 · May 22

What is the "liner" on the inside of the tank spouts there? Some sort of rubber gasket?

Thank you very much for the info.

Freespirit · May 22

I will take a picture of the replacement tank when it arrives but I believe the insert is some type of metal, aluminum? Definitely not a rubber material.

gulfarea · May 22

Looks like they are there to stop the tank spouts from collapsing if to much clamp force is used! I wish I did not have this system as it seems like a lot of extra work over a forced air heater, just my 2 cents, Art

bergger · May 22

I kind of agree with you. I think they should start using the Truma Combi unit. Same size intake/exhaust and will fit in the same space as the Alde. Then remove the Dometic Cool Cat and replace it with the Truma Saphir AC unit. Heat, hot water, and AC all with a single control panel!

pthomas745 · May 22

Today in Costco, I saw a small battery operated hand sprayer that holds 2.5 gallons of water. Fill it with hot water, spray away.

Freespirit · May 23

@pthomas745, the new tank arrived today from NUCAMP, and you can see the metal inserts inside both holes, nice and shiny, compared to my existing tank that was new 2 years ago. I replaced EVERY part of the Alde system 2 years ago with the exception of the boiler and refilled with Rhomar. I was not expecting to see this corrosion so soon(or at all).

fstop32 · May 23

@ReenieG, when I rebuilt my system about 3 years ago I was able to purchase hose from Truma/Alde by the foot. I put totally new hose everywhere. I can't imagine they no longer sell it unless they are having a hard time getting it for their wholesale customers. It might be worth calling them if you haven't yet.

pthomas745 · May 24

@fstop32 Is it possible to compare the material of the metal tubes there in the tank with the material used for the connectors in your Alde hoses? Is the corrosion on the metal the same "type" of corrosion we found at the end of the convector stubs?

This says "something" about the Rhomar, at the very least.

grassgd · May 25

Freespirit said:

@pthomas745, the new tank arrived today from NUCAMP, and you can see the metal inserts inside both holes, nice and shiny, compared to my existing tank that was new 2 years ago. I replaced EVERY part of the Alde system 2 years ago with the exception of the boiler and refilled with Rhomar. I was not expecting to see this corrosion so soon(or at all).

This is very concerning being the first sign of corrosion on the inside of the aluminum exposed to the glycol, in this case the Rhomar fluid. All the corrosion I had and remember seeing reported on this forum has been where the aluminum is covered by the rubber hose.

By chance did you test the Rhomar glycol pH after finding this new corrosion and if so what was the pH?

fstop32 · May 25

@pthomas745 I just browsed through all my T@b pics and I did not have one that showed the inserts to the reservoir tank. My memory does not serve me like it used to but I think it might have been another type of metal, brassy looking maybe. In my case those inserts were "unremarkable" in that they didn't show any corrosion, perhaps that thin white coating I found in the hoses but that's all.
Interestingly, the hose to hose connector parts I purchased from Alde came as plastic unions, not the aluminum ones like were in my 2015 originally.

Freespirit · May 25

@grassgd, I did take some pictures of new Rhomar fluid compared to the 2 year old Rhomar fluid I drained and pH test strips on both samples. The top pH strip is old, bottom pH strip is new. It is hard to see much difference in the pictures but the old looks to be closer to 9 while the new looks to be closer to an 8. The old Rhomar fluid is definitely not as clear as the new

grassgd · May 25

Freespirit said:

@grassgd, I did take some pictures of new Rhomar fluid compared to the 2 year old Rhomar fluid I drained and pH test strips on both samples. The top pH strip is old, bottom pH strip is new. It is hard to see much difference in the pictures but the old looks to be closer to 9 while the new looks to be closer to an 8. The old Rhomar fluid is definitely not as clear as the new

It is surprising that the pH of the old glycol is higher than the pH of the new. I thought as the inhibitor in the glycol is spent or used up the pH would get lower (more acidic).

Rhomar has a product Pro-Tek 922 which is their corrosion inhibitor they use in their glycols.

On the RhoGard information sheet they state:

NOTICE:

When adding less than 50 % RhoGard™ heat transfer fluid to a system, additional corrosion inhibitor should be added to ensure adequate corrosion protection. Pro-Tek® 922 may be used for this purpose.

On their information sheet for Pro-Tek 922 they state:

ADVANTAGES:

PRO-TEK® 922 is designed to provide multi-metal corrosion protection at pH levels of 7.5-8.5 needed for aluminum and copper. When used as directed, PRO-TEK® 922 will prolong the life of hot water systems by reducing the rate of corrosion and help maintain operating efficiency by preventing corrosion debris from fouling the system. PRO-TEK® 922 is compatible with both propylene and ethylene glycol. PRO-TEK® 922 is environmentally friendly.

TESTING:

Fluid pH should be 7.5 - 8.5. Fluid with a pH higher than 8.5 is not recommended for systems with aluminum. Samples may also be sent to Rhomar Water for testing by using the “Water Test Request Form” at www.RhomarWater.com.

ATTENTION:

Exposure to UV or sunlight may cause the blue coloring to fade. This does not affect product performance.

This is a normal recommended practice by a number of glycol manufacturers to monitor the pH of the glycol antifreeze and add additional corrosion inhibitor to keep the pH in their recommended safe range.

When speaking with the National Sales Rep of another brand of glycol that offers a separate corrosion inhibitor to add to or boost the pH, he said the pH should be checked annually. I inquired as to how do you know how much inhibitor to add and if you can overdo it by adding too much. He said it is hard to overdo it and he said they could calculate the right amount to add based on the system volume and how much the pH needs to be adjusted. I asked if it’s time to change the glycol out if the pH doesn’t respond to the added corrosion inhibitor. Said the when the glycol is bad it exhibits an odor caused by bacteria. He also agreed the best way to extend the life of the glycol is to eliminate the glycol exposure to oxygen.

I am working up a method to make the system a truly closed system to minimize the glycol exposure to oxygen. I recently put my system back together but am experiencing problems with the cap on the glycol tank. If you plan on discarding your old glycol tank, I would be interested in having it to work up a good method of making a cap to positively seal and prevent glycol getting out and keeping oxygen out once the cap is in place.

DanWeitzel · May 26

Concerning making your system "closed" you will have to provide a means of controlling the expansion/contraction of the trapped gas in the expansion tank. With our open systems this is the point where free O2 gets pulled into the glycol solution every time the system goes thru a heat/cool cycle. Here is a thought; replace the expansion tank cap with a balloon making sure there is a tight fit on the tank filler neck. To eliminate any O2 in the tank, purge the tank with N. I would do this on a cold system with the balloon just very slightly inflated, this way it will never go negative and get sucked into the tank. As the system heats up the balloon will expand, hopefully not too much. Probably need to repeat the cycling of O2 out N in several times to insure all/any O2 has been replaced by N.

BridgerSunset · May 26

Thanks for the effort @grassgd. I think this is some good science.

I concur that fluids with low or high pH both cause corrosion issues, in the absence of corrosion inhibitors. And introducing oxygen to water-based conductive fluids absolutely invites accelerated corrosion. I've seen how oxygen can eat through almost 1/4" thick carbon steel in a matter of a few months in a heated service environment.

The white stuff everyone sees is very likely aluminum oxide, the by-product of corroding aluminum.

Anything we can do to maintain corrosion inhibitor life ( i.e, replacing glycol) , and to eliminate oxygen entry (either at the glycol tank cap, or at the convector stub clamps) is good practice.

grassgd · May 26

DanWeitzel said:

Concerning making your system "closed" you will have to provide a means of controlling the expansion/contraction of the trapped gas in the expansion tank. With our open systems this is the point where free O2 gets pulled into the glycol solution every time the system goes thru a heat/cool cycle. Here is a thought; replace the expansion tank cap with a balloon making sure there is a tight fit on the tank filler neck. To eliminate any O2 in the tank, purge the tank with N. I would do this on a cold system with the balloon just very slightly inflated, this way it will never go negative and get sucked into the tank. As the system heats up the balloon will expand, hopefully not too much. Probably need to repeat the cycling of O2 out N in several times to insure all/any O2 has been replaced by N.

My first thoughts were to do exactly as you say including purging oxygen out every time the tank cap is removed for any reason. Although that is possible if you kept a small tank with nitrogen or other inert gas on hand to do so.

A more practical solution is to leave any oxygen that gets in when the cap is removed but prevent the constant breathing and bring in additional oxygen all the time. This minimizes the amount of oxygen that gets into the system especially if you don't open the cap on the tank unless necessary.

Either way, sealing the system up and providing a method to handle the expansion would be beneficial.

grassgd · May 26

BridgerSunset said:

Thanks for the effort @grassgd. I think this is some good science.

I concur that fluids with low or high pH both cause corrosion issues, in the absence of corrosion inhibitors. And introducing oxygen to water-based conductive fluids absolutely invites accelerated corrosion. I've seen how oxygen can eat through almost 1/4" thick carbon steel in a matter of a few months in a heated service environment.

The white stuff everyone sees is very likely aluminum oxide, the by-product of corroding aluminum.

Anything we can do to maintain corrosion inhibitor life ( i.e, replacing glycol) , and to eliminate oxygen entry (either at the glycol tank cap, or at the convector stub clamps) is good practice.

I was wondering what the white stuff found on the id of the aluminum parts and the rubber hoses was. If it is aluminum oxide, I can understand it being on the inside of the aluminum pieces, but would it actually get deposited on the rubber hoses?

If it is aluminum oxide from corrosion, the corrosion appears to be uniform and not the same as what is happening under the rubber clamped areas.

I saved some in a jar and would love to test it somehow to confirm if it's aluminum oxide or something related the corrosion inhibitor that gets deposited on everything.

DanWeitzel · May 26

I failed to remember the vent on the expension tank is NOT on the cap. Sealing the cap tightly and then using the balloon on the small vent would be a means of stopping the O2 exchange cycle. As long as there are no leaks there shouldn't be many reasons to open the cap thus allowing the N to escape. You still need to have some way for expansion on heat up to prevent pressure build up in the system.

Image: https://us.v-cdn.net/5021717/uploads/editor/wa/2b5ux3rumsqc.jpg

grassgd · May 26

DanWeitzel said:

I failed to remember the vent on the expension tank is NOT on the cap. Sealing the cap tightly and then using the balloon on the small vent would be a means of stopping the O2 exchange cycle. As long as there are no leaks there shouldn't be many reasons to open the cap thus allowing the N to escape. You still need to have some way for expansion on heat up to prevent pressure build up in the system.

My tank actually has two tubing vents. One is lower which apparently is intended to be a glycol overflow while the second one appears to be a simple vent. Both have a metal insert inserted in the tubing to facilitate a tight fit to the tank but the tubing gets hard and does not make a good seal on mine.

I replaced these metal inserts with a proper barbed bulkhead type fittings to connect the clear tubing to the tank. A better tubing might be to use a epdm rubber hose to avoid the tubing from getting hard over time. I may change out the tubing for the epdm rubber in the future.

I connected both tank vents together and ran it to a simple separator which will collect any glycol and allow it to go back into the tank as the glycol cools. The vent off the separator then goes to a bladder to account for vapor expansion off the glycol tank/separator.

I am still working on a replacement arrangement for the poor fitting cap on the glycol tank.

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