Corrosion of Alde Convectors

Mickerly · May 2021

I've been watching this for a while. The HotRod community has the same issue with custom cars with custom Aluminum radiators. The corrosion happens in the stagnant fluid trapped under the hose connection. The radiator manufacturers recommend using a light coating of silicon plumbers grease on the metal. A light file is all that is needed to prevent or significantly slow the corrosion process.

BrianZ · May 2021

@ScottG, here is a shot of that nasty looking corrosion you commented on, but after cleaning. There is indeed some pitting, but it's not quite as bad as it looks at first, and I was wrong - it was a side convector. These are the areas I think will benefit from the conformal coating before the heat shrink tubing goes on..

PS: In the above photo, note that this area of our worst corrosion is facing the mounting & the wall it's mounted on, and could have been overlooked or inadequately treated if I hadn't removed it. Admittedly,though, I initially removed them for convenience in accessing them for cleaning.

Unfortunately, the inside under those bad areas is showing signs of corrosion in two spots (below), but very small. I'm thinking it's best not to mess with them as far as cleaning, but not sure about using the conformal coating there. Maybe it could help.

Here's another with pitting on the outside & small areas of early corrosion on inside..

Overall, the pipes seem strong & intact, so I still consider these early signs & hoping the process can be arrested or at least significantly delayed.

Finally, this shot above is for you, @ScottG, to show some of our pipes do have a very fine layer of whitish coating which can be scraped off. The ones I showed before I think were at the Alde or a connector at the check valve. I'm guessing this is some form of corrosion, but whether it is the primary site in a more distributed pattern or just being deposited from somewhere upstream might be another question.
Any votes for coating the small inside spots with the conformal sealer? I'm inclined to do it.

ScottG · May 2021

Thanks for he additional photos, @BrianZ. I'm thinking now the differences I'm focusing on inside the tubes may just be a matter of time and age (six years as opposed to three). I still don't know what to make of it, but I'm doubting more my wishful hope that the hard deposits were indicative of anodizing--at least on the inside.

In any case, these do seem to be clear cases of deposit corrosion originating on the outside of the pipes. I have no authoritative opinion on any of the proposed mitigation strategies, but all seem reasonable if one has the abiity and the inclination to make the effort.

I tackled my glycol exchange early in this discussion. If I had it to do over, I would probably have inspected things a little more closely and perhaps taken more aggressive steps to address the corrosion I did find. However, at this point everything is back together and working fine, so--unless something dramatic happens--I'm disinclined to tinker with it further with it until my next glycol exchange.

Hopefully by then we will have a little better handle on the situation, and maybe even some official word from Alde or nuCamp. Given the number of cases popping up, it's becoming pretty hard to imagine nobody on that end knows what is going on. In the meantime, keep the reports and ideas coming!

ScottG · May 2021

Mickerly said:

I've been watching this for a while. The HotRod community has the same issue with custom cars with custom Aluminum radiators. The corrosion happens in the stagnant fluid trapped under the hose connection. The radiator manufacturers recommend using a light coating of silicon plumbers grease on the metal. A light file is all that is needed to prevent or significantly slow the corrosion process.

This sounds like a very similar situation, and the plumber's grease would certainly be an easy step to take.

@Mickerly, I assume you meant a light film (as opposed to a light file).

While on the topic, what (if anything) does the hot rod community do to remove or clean up corrosive deposits that get trapped under the hoses? I just used a little water and a light scrape with a Scotch Brite pad, but wondered if there was something more aggressive I could have attempted.

BrianZ · May 2021

Here is one more photo showing cleanup work I did on the bleeder valve and associated aluminum connectors in the corner
to the left of the upper rear convector..

Before cleanup, the valve was covered with green & white deposits of corrosion & the thumb-screw valve was frozen & difficult to unscrew. I soaked it for a couple hours in vinegar & cleaned with water & a toothbrush. After drying thoroughly, I coated the whole valve body with silicone conformal solution, which dries flexible & shiney, being careful not to get any in the drain hole or in the thumb screw threads. After drying, I then used a toothpick to apply some silicone plumber's valve grease to the couple of threads (arrow) exposed by fully opening the valve, so it works smoothly again.

For the corrosion on the aluminum tubes, I just used a shiney stainless scrubbing "wool" pad to clean them up & coated with conformal coating for corrosion protection. I will skip the heat shrink tubing on these, due to the extra difficulty in getting the rubber hoses back on in this tight corner.
Still need to move the hose clips back over the tubes.

fstop32 · May 2021

Hey @BrianZ, I'm back home from backpacking in CO now and getting caught up on forum news. When I saw your pic of the heat shrink on the convector pipe I really liked that idea, but I did want to ask how much harder it was to put the hose over it as it looked a bit thick (which I like that it looked substantial)?
Great posting on your process btw! Maybe by the time I get parts we'll have all this figured out

BrianZ · May 2021

Yes, I still like that heat shrink tubing, particularly because the inside has an adhesive coating so it won't shift when you put the rubber hose over it. It makes a a bit more trouble to put on, but not that difficult - you just have to approach at a bit more of an angle & then wiggle it side to side. Where I struggled a bit more was getting the original clips back on over the thickened hose - not much free space between clip & hose, even with the clips fully squeezed open. What made that difficult was in the back corners where there's not much space & I needed to get a second hand on the clip to try to push it sideways. Not much wiggle room. I succeeded though, and I think the extra protection is worth the effort.

Here's the coating I used on aluminum connectors and the plumber's grease, which is a thick clear grease..

This exact conformal coating wasn't available from my original source, which might be a good thing since it's got some nasty volatile solvents (toluene, xylene etc) that requires careful use & outdoors (pathology labs don't even use these dangerous solvents anymore). But it dries extremely fast & makes a nice smooth, durable, waterproof nonconductive coating.

I found more corrosion on this connector tube returning to the expansion tank elbow. Where you see the two spots here, there were matching ones inside..

And for @ScottG, notice the white deposit is coating the inside of the non-corrosive rubber hose, as it is in the metal tube, but where it originated is a good question - maybe from all the aluminum tubes.
I decided to get more aggressive with cleaning by using the metal curly mesh stainless scrubbing pad to quickly clean it up before coating with conformal solution..

I scrubbed & coated the inside spots too.
For anyone using new connector tubes, l would recommend using a conformal coating &/or adhesive heat shrink tubing for corrosion prevention.
My last piece to go back on! Hallelujah! Now I can actually use my new 3-way valve to give a final rinse & leak test with a few more gallons of distilled water, then refill with Century glycol, and I'm done for a couple years. Then, it should be a much easier task to just connect the pump to the valve & bottom-fill the system by pushing out the old stuff with the new.

fstop32 · May 2021

Quick question that maybe should be somewhere else, but... Since I may not get the parts I need in time to rebuild my Alde system can I use my 320 on a planned trip for hot water purposes? Can I reinstall my Alde boiler with glycol in the glycol jacket and the input/output pipes blocked off with rubber caps and use it safely as a hot water heater?

Mickerly · May 2021

The plumbers grease, mostly silicon. What I purchased at ACE was 95%.

I understand a scrubby, wire brush type of work to remove the old corrosion. Then a light wiping of the silicon will leave a film that will prevent new corrosion.

Make sure you look at the tubing to make sure the corrosion hasn't eaten through to the inside.

ScottG · May 2021

fstop32 said:

Quick question that maybe should be somewhere else, but... Since I may not get the parts I need in time to rebuild my Alde system can I use my 320 on a planned trip for hot water purposes? Can I reinstall my Alde boiler with glycol in the glycol jacket and the input/output pipes blocked off with rubber caps and use it safely as a hot water heater?

@fstop32, I would be hesitant to try this. The glycol jacket needs to be completely full, and since the Alde is not normally a closed system I would expect expansion of the glycol to cause a mess at best, and core damage at worst.

Now, if you could somehow hook the input/output pipes back up to the expansion tank, I'd be confident that would work. This would ensure the boiler stays full and the glycol has room to safely expand--just as it does in normal operation. The only difference is that there won't be a convector loop.

This was going to be my back-up plan for hot water had I found my own convectors unsalvageable.

fstop32 · May 2021

Good point @ScottG, I might have enough stuff on hand to do that if it comes to it.

BrianZ · May 2021

I just got our system restored yesterday & tested with heat this morning. Here are the before(cold, lower) & after(hot, higher) levels in the tank..

I still need to top it off a bit.

PS: @fstop32, here's some hose that should work, sold by the foot, but expensive..
https://www.amazon.com/dp/B07YNG292X

BrianZ · May 2021

ScottG said:

...
Century and other sources have repeatedly claimed that pH is indeed related to the effectiveness of the corrosion resistance, though a pH of 8 is probably on the low end of acceptable and may suggest the start of degradation. Most who have tested their Century glycol (including me) get a pH closer to 9.5. Whether there is something going on beyond what pH indicates has yet to be confirmed. In contrast, freeze protection is typically checked with a refractometer calibrated for propylene glycol.
...

I find this issue of pH very interesting, both with reference to the glycol solution, its secret additives (which seek to adjust the pH), and the relationship of pH to the corrosion process.
Apparently, when aluminum is exposed to oxygen, it immediately forms a microscopic protective layer of aluminum oxide, and this layer is stable within the pH range of about 4 to 8.5 (see https://www.google.com/amp/s/www.chardonlabs.com/resources/aluminum-corrosion/amp/ )

Many of us have measured the pH of our green Century TF1 glycol to be around 9.5, which begs the question of why they would do that. Apparently glycol has a relatively neutral pH, but added buffers seek to make it more alkaline (maybe to offset possible microbial contamination? Who knows, it's proprietary, right?).

In looking at the data sheet of the new blue glycol, it lists a pH of 7.5 to 8.5. Well, that's interesting - the same upper limit at which the protective aluminum oxide is reportedly stable! Hmm.
(https://nucamprv.freshdesk.com/support/solutions/articles/44002156353-2021-glycol-change
https://nucamprv.freshdesk.com/helpdesk/attachments/2043191143178)
The secret ingredients are listed as "alkaline filming corrosion inhibitors, dispersant and reserve alkalinity booster". Aluminum oxide is a white solid or powder - is that the film I found covering the inside of my black rubber Alde hoses?

Did the original glycol buffers at roughly pH 9.5 just overshoot the pH limit by one pH unit, just enough beyond the pH 8.5 limit to allow some corrosion to start? If so, then I'm not surprised that they have this new formula. Good thing we don't need a proprietary pH meter to test it, but I'd be interested to hear from anyone with the new blue glycol fluid & a pH meter or strips, what is your glycol's pH?

It's also interesting that corrosion occuring on the alkaline side of the range limit of aluminum's stability is more typically the pitting type that we've seen on our convector pipes (per the first reference).

pak · May 2021

Good info, thanks

ScottG · May 2021

That is an interesting discrepancy, @BrianZ, and certainly seems to fit the pattern. It's also a bit out of my pay grade so I can't comment further with any authority. It seems there should be a reasonable explanation--if not, the decision to use corrosively alkaline transfer fluid was a pretty whopping oversight.

Tabaz · May 2021

New blue fluid right out of the factory container (not my T@B). Just noticed my test strips expired in 2013, so don't know if that affects the test result. Looks to me to be about 7.5.

Image: https://us.v-cdn.net/5021717/uploads/editor/ku/g5gm7zfgrqsh.jpg

BrianZ · May 2021

Tabaz said:

New blue fluid right out of the factory container (not my T@B). Just noticed my test strips expired in 2013, so don't know if that affects the test result. Looks to me to be about 7.5.

Thanks, @Tabaz.
I would be more excited about this result if the test strips weren't expired for 8 years. Thank you though, and please repeat if you get new strips, or let me know if you can try your test strips on solutions of known pH of around 6 and 8, that may indicate whether they are still working.

BrianZ · May 2021

@Tabaz , here's what you could do to check your test strips..
Put a half cup of water in each of two small cups. Add 1 tsp of [white] vinegar to one and 2 tsp of baking soda to the other and stir until dissolved. This should give you solutions with a pH of about 4 and 8 respectively. I'd be most interested in what you get for the baking soda one.

Tabaz · May 2021

Brian - I'll pick up some new strips on the way home tonight and retest.

Tabaz · May 2021

Image: https://us.v-cdn.net/5021717/uploads/editor/x8/6rmdkpqy1n75.jpg

Brand new bottle of pads. I'm color blind so I'll leave it up to you to decide where the strip bests matches the chart.

BridgerSunset · May 2021

Here's another dataset. 2 sets of 2 tests from the 5-gal jug of Rhogard. Strips expire 11/2022.

Image: https://us.v-cdn.net/5021717/uploads/editor/xv/0sw02rvw51gg.jpg

BrianZ · May 2021

I agree, @Tabaz , it looks like about 7.5.

BrianZ · May 2021

Hmm, these are tough, @BridgerSunset.
Maybe around 8?

BrianZ · May 2021

Note: I used my photo editing software to perform some digital color sampling of these images, and the closest color matches for both sets of images were the color/pH squares on either side of my own interpolated numerical choices above. To avoid sampling error due to pixelation within each color square of these low-res images, I had to blur the image to average out the color across each square before sampling, which then selects the position within the color spectrum & hex value of each sampled color to compare.

Tabaz · May 2021

Ugh, BrianZ (if that’s your real name), your last post above is a little disconcerting. Most humans don’t talk like that. With the recent spat of confirmed UFO sightings, I’m just wondering if your not “a Brother from Another Planet.” I’ll leave it up to the forum moderators to decide if Federal authorities should be alerted.

Dalehelman · May 2021

If you are going to change the Century fluid every 2 years. Why is the ph level of any concern?

ScottG · May 2021

@Dalehelman, it's not convincingly clear that changing the glycol every two years will guarantee that this problem will not occur. Also, if the pH is corrosively alkaline from the start (and I'm not claiming it is or isn't) than one would expect corrosion to begin immediately (albeit slowly) on contact.

ScottG · May 2021

Tabaz said:

Ugh, BrianZ (if that’s your real name), your last post above is a little disconcerting. Most humans don’t talk like that. With the recent spat of confirmed UFO sightings, I’m just wondering if your not “a Brother from Another Planet.” I’ll leave it up to the forum moderators to decide if Federal authorities should be alerted.

@Tabaz, haven't you been following the mods @BrianZ has been making to his T@B? He says they are all about "changing the glycol" but I suspect something of a more otherworldly nature...

Slackers · May 2021

Resistance is futile. You will be assimilated.

BrianZ · May 2021

Haha, my apologies @Tabaz . I do enjoy a challenge though, even if it's just academic (and a laugh!

).

@Dalehelman, you're right, it's not going to change my plan going forward, now that I've cleaned up our corroded parts, protected them with chemical & physical coatings from further corrosion, and installed a new valve to make future glycol flushes much easier to keep up with. So we're all set.

I'm curious by nature, and just want to understand why we've had these corroded aluminum parts and why the new glycol might be more compatible with the Alde system (& how the old glycol may have contributed to the corrosion). Yes we are partly to blame too for not keeping up, but it's not exactly easy to get service or support for this either. I'm very thankful to Nucamp & contributors for this forum, however.

If you read my May 25th comments, there is evidence that a pH between 4-8.5 can be more protective for aluminum, so you may be better off with a pH of 8 for example. If the new glycol is within that range, this may help explain why the company switched glycol & why the old glycol with its pH of about 9.5 might not be optimal for compatibility with aluminum & possibly depends more on its corrosion inhibitors with limited life for more limited protection. I could be wrong, but data seems to support this idea.

It's mostly just academic to me at this point, unless it becomes more economical in the future to switch. But then there's the "GRAS" issue, which makes me not want to switch to something if it's any less environmentally safe. The current glycol is at least biodegradable - not sure about the new stuff or why it's not GRAS, if that's the case.

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