Alde Glycol Tank Anode Rod Mod

BrianZ

In another topic, I had posted links to a couple of videos that introduced the concept of installing an anode rod (like those used in water heaters) inside the glycol expansion tank, in order to help prevent galvanic corrosion in the Alde system.  Here's the link to those..

https://tab-rv.vanillacommunity.com/discussion/comment/172946/#Comment_172946

While this is acknowledged to be an experimental idea, I thought it sounded like it has the "potential" to help with corrosion in the Alde heating system, so decided to give it a try, since I'm already familiar with doing this for our home water heater.  

Here is the anode rod I got for this project.. https://www.amazon.com/dp/B07XK6PM39

which I cut with a hack saw to fit inside the tank.

The photo below shows how I prepared the anode rod to fit inside the threaded cap of the glycol tank.  I saved the plastic disk top inside the threaded part of the cap & replaced it with a disk cut from a sturdy plastic bottle.

Because it is difficult to solder a wire onto a flat surface (which I roughed up with coarse sandpaper) and get a strong joint, I also mixed up some JB Weld epoxy glue and added that on top fo some extra strength..

I ran the 18g wire into the corner to the floor..

then through the rear storage compartment inside a piece of narrow plastic conduit to keep it from getting tangled up with other stuff..

Then I ran it through the same opening as the Alde hoses and into the Alde compartment, again inside a piece of stick-on plastic conduit..

Using another circular wire connector soldered to the end, I fastened it to one of the screws holding the gas line fitting to the Alde chassis..

And that's it!

If you do this, and have a voltmeter, before you hook it up, I'd be curious to hear how much voltage you measure between the end of this wire and the the Alde screw.  I'm wondering now whether the reading might be more steady with the glycol circulating.

By the way, did you know that in the past, T@Bs used to have a water heater anode rod?  See the Tab manual link given here by Wanderoo..

https://tab-rv.vanillacommunity.com/discussion/comment/4893/#Comment_4893

I assume this was an anode in the hot water tank itself (and probably not an Alde), as in a home water heater, and not the glycol tank like we're talking about here.  Still, it does make me wonder why the Alde never had one.

Happy Turkey day!

Sharon_is_SAM

@BrianZ - from the “Changing out the Alde fluid” discussion regarding the anode rod mod, you questioned the issue of sediment:

“The only reservation that I might have is whether any sediment that falls off the corroding rod would safely make its way out of the tank & down into the drain hose, without getting sucked by the pump back into the Alde.  Water heaters normally have a bottom drain for flushing any sediment out, but they don't push out hot water from the bottom, but a bit higher up off the bottom.  With such an anode installed, it might be worth periodically opening the drain to let out a couple ounces, before ever increasing the Alde pump speed.”
Any further thoughts?

BrianZ

Thanks for adding that, @Sharon_is_SAM, a good reminder, because I would expect pieces of the corroded anode rod to eventually start falling off.  It could take years though, so I'm wondering if there would even be a significant amount actually falling off by the time the semi-annual flush comes due.  Also, the rods are relatively cheap, so could be replaced as part of the glycol service routine, if needed.  One other note, it's easy to take the cap off the glycol tank & check the condition of the anode, something that can be a real chore on a home water heater, where you may need an impact wrench to loosen it.  The thought of replacing the rod makes me think it may be better to use a clamp instead of soldering the wire to the rod.

ScottG

Nice work, @BrianZ (as always). Your post on this topic is timely. 

I just watched the video series you mentioned. The more recent comments--including yours--were also informative.

Engineer Mark (the guy who makes the videos) doesn't directly address the crevice corrosion on the convector stubs. He mentions in the first video that some owners have reported corrosion in these locations, but never explicitly reveals the state of his own T@B.

In the comments--and in the second video--he touches on the different types of corrosion, implying that what is going on at the convectors is acidic corrosion and will not be mitigated by the anode rod (which combats galvanic corrosion). He suggests that regular changing of the glycol (to maintain the pH) is the key to preventing this, but now we are back where we started... owners who have tested their glycol have found it retains its high pH (i.e., it is NOT acidic) even if neglected for some time.

My guess--and it's not much more than that--is that the convector problem is a type of acidic corrosion stemming from a combination of fluid stagnating between the hoses and aluminum convectors, that fluid drying/crystallizing (and possibly becoming acidic at the point of contact), and the direct contact eating away at the metal over time. If that is the case, then I suspect properly sealing the hose-convector connections is the best strategy for this particular problem. Given that Alde appears to offer a sealant for just such a purpose adds credence to this idea.

This is not to say the anode won't possibly protect against other more elusive galvanic corrosion issues inside the boiler itself, but I suspect it is another red herring in this case. The same may be true for often discussed concerns about properly grounding the Alde--while this may combat the electrical corrosion Mark also mentions in passing in the second video, it may not solve the convector corrosion issue either.

Just some food for thought while we await food for bellies. Happy T-Day, all!

MarkAl

I've thought about this mod since seeing Mark T's video on FB but on the 2021/22 model 320 the bottle is in the front (toilet) area - that's a tough run to do for the ground wire. But I would think any close convector would work as well. Though this brings up the thought that each convector & Alde should be connected together through the chassis ground. Thoughts, though I'm bracing to also seal the hose to pipe with either grease and / or sleeve. There's some discussion that bulging is happening even on the more recent models and we use our heater a lot in the spring / fall / winter.

RCB

To have half a chance of stemming possible galvanic corrosion; all convectors, Aldi boiler, Hot water unit, must be connected to the anode. This is common on boats - thru hull fittings, engine, prop shaft etc. are all wired to the in the water anode. I’m not sure what the best anode might be for the transfer fluid. Again, in boats anodes are now aluminum or magnesium depending on the salinity of the water. Zinc is now used to a lesser degree.

BridgerSunset

@ScottG  I tend to agree with your synopsis.... and will add these thoughts-

High pH isn't good either.  It is at least as corrosive as low pH (acidic) on aluminum. 

Numerous studies in literature show that the protective aluminum oxide film (which forms when immersed in air or in an aqueous solution) that is stable near a neutral pH range is dissolved away when pH readings are outside that range - both lower and higher.  And corrosion rates are shown to be accelerated by immersion time, temperature, and to some extent, salinity.

Since the new Rhomar is at a pH nearer 7.0 - 8.0 from the get-go, as @BrianZ and others surmised, I too believe the switch was needed because the Century was seen as ineffective on aluminum under certain conditions, both initially and especially when the buffers/surfactants/inhibitors were expended.  It may not entirely be the root cause of these failures, but it sure is a factor.   Oxygen in the system, under-deposit-attack, surface irregularities may also contribute.

Aluminum being what it is, is already prone to metal loss, even in the best of conditions.  The stagnant areas are an easy mark for metal loss, because there's a lot going on there to contribute to the corrosion process.    The rest of the system at least has the advantages of being a large "anode" with more surface area that hopefully spreads out the pitting if corrosion is inclined to happen there.  Plus it sees moving fluid with hopefully constant corrosion inhibitor replenishment while in use.

The fact that some pretty new systems are showing signs of this corrosion is something Alde/Truma needs to explain, because I'm pretty sure they are aware of the reasons.

Scrunchy

Quick question, should we ground the heater coils also? Fluid flowing inside may cause a difference of potential? 🧐

BrianZ

Thanks, @ScottG, and others for your contributions on this topic.  I want to acknowledge that I didn't do this mod to address any issues with convectors, but to maybe address possible corrosion in the Alde itself in case that could be an issue.  As noted, one would need to wire up the convectors too for any protection from galvanic corrosion, but that likely still wouldn't address the primary issue with crevice type corrosion & pH issues under the hoses, which I've already addressed with physical barriers.
Thanks for reminding us, @BridgerSunset, that corrosion in a system is also a balance depending upon the total surface areas that come into play.
If I see significant anode corrosion before the next glycol exchange is due, I would remove it & try to clean with a brush & possibly drain a few ounces to remove any sediment & top off.

Freespirit

This may be old news but here is a link to an update on Mark’s T anode rod installation. 

Hope I copied the link correctly and it works?

https://youtu.be/HcUqcYii7XQ

cheers

BrianZ

Yep, worked for me, @Freespirit, thanks.  His list of 6 thoughts in the comment section are interesting too, about what he has found after 6 months & what he expects to find later on.  It sounds like he doesn't expect sediment to be a significant issue within the 2 year interval between glycol changes, and I hope he's right. 
I was especially curious about his statement..
"I expect to find that the other metallic 

components in the system will have likely picked up a single molecule thick electroplating of protective magnesium themselves."
OK, but how will he find that?

In any case, like I said, it should be easy enough to check the anode periodically, and if it looks like corrosion could be flaking off, then it could be cleaned up or replaced, which is much easier & cheaper to deal with than corroded boiler parts.

ScottG

@BridgerSunset, thanks for your comments--particularly the reminder that the pH of the Rohmer glycol is notably lower (i.e., more neutral) than that of the Century product. It makes sense that alkaline solutions can also contribute to corrosion, and your assessment certainly fits with the evidence (however limited) that we have thus far.

BrianZ

To followup on my last comment about corroded boiler parts, I was recently reminded of one part in particular by an article about hot grounds referenced by @Sharon_is_SAM in another topic on EMS systems..  A corroded part shown in that article was a heating element from a water heater, and in the case of the Alde, we have heating elements immersed in the same glycol being protected by this anode rod.  As the article notes, a failed heating element could send a high current where you don't want it, so corrosion protection can be a major safety concern.

PS:  Unfortunately, I don't think the heating element is protected by the anode rod, if it doesn't have electrical contact with the Alde cabinet.

DanWeitzel

I have also installed the anode in our 2016 T@B.  When checking about 6 months after installation I found some slight degradation of the anode (Alde system was not being used during this time).  I also checked the pH of the transfer fluid: New = 9.0, current fluid in the system (6 months old) = 8.5.  I cleaned the anode & reinserted it, will keep an eye to see if any changes now we are in heating season.

BrianZ

Thanks for sharing your photo documentation, @DanWeitzel.  I would think that pH 8.5 would be better for less chance of corrosion of aluminum parts than at higher pH levels.  It looks like you have some significant signs of corrosion, not a large amount, though enough to see the anode is doing its job.

BrianZ

This is my 5-month update after installing a sacrificial magnesium anode rod inside our glycol expansion tank.  As you can see from the next couple of photos, there is significant corrosion visible on the anode where it is submerged in the glycol fluid..

There is a buildup of whitish crystalline material adhered to the rod, some of the more superficial of which can be easily dislodged with handling, while the majority of crystals in closer contact with the metal are difficult to remove.  

Another observation I found interesting is the lack of any corrosion deposits near the bottom of the rod.  One explanation might be that the oxygen level may be lower at deeper levels, as oxygen is a primary contributor of electrons in the galvanic corrosion of an anode.  

The end of the rod extends into the recessed area where the return flow of glycol enters the tank; however, the Alde & pump are turned off most of the time, so any mechanical effects of the rate of flow into that narrow channel are not present most of the time.

I was able to clean the deposits off by using a medium grit sandpaper, as shown below, except for some discoloration.

After replacing the anode in the tank for two days, I removed it again to get some measurements, when I noticed the thin line that had developed at the liquid level in the tank, which can be seen in the next photo.

In the next photo, I overlaid a photo of the anode rod on an old photo of the tank assembly, just to show its relative size & how far the 7-1/4" long anode rod extends into the tank.  I had cut it as long as possible to give maximum surface area in the glycol.

The rod extends about 3/4" into the recessed area of the tank located directly below the cap, where the return hose attaches to the bottom of the tank.

I didn't really find anything surprising at this point.  There was a significant amount of corrosion on the anode, so it is doing its job by sacrificing itself to presumably help preserve the internal Alde metal parts.  In 5 months though, it showed a level of corrosion that is similar to that found on our convector stubs, which took 4+ years to develop (albeit by the different mechanism of crevice corrosion where local pH changes becomes a factor, versus the galvanic/bimetallic type from which sacrificial anodes are intended to protect).

There was this one surprise though (at least to me at the time), shown in the photo below where I detached the anode wire from the screw in the Alde case, to measure the open circuit corrosion voltage..

The galvanic potential of this anode generated a voltage of 1.06V, like a little battery.  Now, from what I've been reading, it could have been even higher, but there are many variables at play in such a system.  I could not measure any current though, presumasbly because it was too low, as galvanic corrosion is a slow process, taking weeks, months or years.  As noted in the following video at the 2 min mark, the instantaneous measurement of the corrosion current may be in the micro-amp range and requires a special device called a potentiostat..

https://youtu.be/z3JjcDncEJc

I have a high quality Fluke meter, but its resolution only goes down to within a few milliamps, which is just not sensitive enough.

I am feeling better about concerns regarding solid particles of corrosion deposits falling off into the glycol.  I observed only a relatively small amount of tiny corrosion particles coming off the anode rod, and that was with handling while trying to dry off the glycol fluid with a paper towel.  I would expect any of these tiny pieces to be easily flushed out during the routine glycol flushing service.  Since the anode rod can be easily removed from the tank for inspection, it can also be relatively easily cleaned of corrosion buildup (though that may change significantly in a couple years & require replacement).  To facilitate easier removal of the anode for inspection or cleaning, I plan to either switch from a soldered connection to a clamp, or else cut the wire a few inches from the solder joint & install a spade type connector in the line for easy removal.

One other "potential" issue remains as to whether there would be any interference with this anode circuit by installing a new Alde grounding wire (as per the Airstream update procedure referenced in other topics) to the same location on the Alde cabinet where the anode wire is connected.  I don't think so, but I also plan to share my ground voltage measurement results on that topic soon.

Dutch061

@BrianZ

I had posted the results of my testing with a magnesium anode this past week in the thread about corrosion earlier today. Based on the tripling of the voltage measured at the convector under the floor of the shower (TAB 400 BDL), and the tripling of the current flow .2 micro amps VS .7 micro amps. with the anode connected to ground, I decided that adding an anode was not the correct decision for me, but I respect the decisions and opinions of others to do so.

Airstream makes no mention of an anode in their bulletin. I suspect there are way more Alde systems installed in the Airstream population than NuCamp, but I could be wrong.

I think most of the issue goes back to the 8-gauge ground wiring that Airstream specifically says to replace with 6-gauge. This is further driven (my opinion) by how the camper is being used, IE shore power VS boondocking. And by adding the auxiliary ground wire to the boiler case just ensures that there is a path to ground for the glycol, even though it has a very high resistance. 

Brad

BrianZ

@Dutch061,
Thanks, Brad, I saw that, and plan to add my ground measurements there, based on your previous suggestions, plus a few thoughts on your anode report.  I'm still trying to catch up on the writing & posting part of what I've found, but been busy with taxes & stuff lately.  How are you measuring microamps?

Dutch061

@BrianZ

I used a DMM that has a micro amp scale, how accurate is a question that I can't answer. But I can easily see the measured voltage between the under-bath convector go from 256 MV to 750 MV with the anode connected to ground VS not connected. To me, this indicates that a higher number of electrons are moving from the convector into the glycol, which is the exact opposite that I had thought or wanted.

Brad

BrianZ

@Dutch061,
I think the answer may be to ground the convectors also, as some have done.  The anode rod in the glycol tank can only protect what it's grounded to (or metal shared in common plus in the glycol/ electrolyte), and in the linked video by Mark he clearly (& correctly) says it won't protect the convectors without a common ground with the anode, just internal Alde parts.  So it wasn't intended to protect convectors.

DanWeitzel

Following these posts with interest.  I installed the anode rod last year and have seen the same results as to the crystalline material adhered to the rod.  This was only several months after installation and most of time the
the Alde was not in operation.

  

YanniLazarus

Dutch061 said:

@BrianZ

I had posted the results of my testing with a magnesium anode this past week in the thread about corrosion earlier today. Based on the tripling of the voltage measured at the convector under the floor of the shower (TAB 400 BDL), and the tripling of the current flow .2 micro amps VS .7 micro amps. with the anode connected to ground, I decided that adding an anode was not the correct decision for me, but I respect the decisions and opinions of others to do so.

Airstream makes no mention of an anode in their bulletin. I suspect there are way more Alde systems installed in the Airstream population than NuCamp, but I could be wrong.

I think most of the issue goes back to the 8-gauge ground wiring that Airstream specifically says to replace with 6-gauge. This is further driven (my opinion) by how the camper is being used, IE shore power VS boondocking. And by adding the auxiliary ground wire to the boiler case just ensures that there is a path to ground for the glycol, even though it has a very high resistance. 

Brad

Can you explain your comment about "how the camper is being used"?  Less or more corrosion with boondocking? Any corrosion issues with leaving the T@B on shore power with the Alde off?  Thanks. Trying to decide if the anode makes sense... or if trying to understand upping the alde ground wire gauge is sensible.