Water heater, anode rod, electrolysis, and teflon tape

[BB_TX]

It is often stated on RV forums that you should not use teflon tape on the anode rod threads as it could interfere with the electrical contact. Being fairly knowledgeable in electric (retired EE) and limited knowledge of electrolysis, something just did not sound right. And my little engineering brain can't live like that. And finding nothing definitive by googling, I went directly to the source. I e-mailed Suburban with my question, "Does the anode rod threads have to make electrical contact with the water heater threads for the anode rod electrolysis to work properly?"

I got a quick reply from an assistant service manager at Suburban as follows;

"The answer is No. The metal threads do not need to make contact with each other. Electrolysis is the chemical reaction that takes place inside the tank and has nothing to do with the threads. I've attached some Suburban water heater videos to this email that I believe you'll find very interesting."

And here is the video they attached, actually using the tape. So those who use teflon tape can rest easy.

Suburban water heater video

[fj12ryder]

Ah, I think I see where the fallacy lies: "The connection can come thru the electrolyte." But it has to be a strong enough electrolyte, plain water in the hot water tank isn't really a strong enough electrolyte to contain enough free ions to work well.

So the Suburban guy is correct in general, but incorrect specifically.

[BB_TX]

After again posing the question to Suburban I got a response from their senior product engineer as follows;

The two metals only have to be electrically connected, not physically connected to one another. The connection can come thru the electrolyte. I’ve attached some light reading on the subject from Materials Science and Engineering: An Introduction 5th Ed.

So I will leave it at that. Functionally for the RV water heater it is a moot point as I have always used tape on the threads and upon removing the rod there has never been more than strings of tape left after the threads cut, shredded, and compressed the tape into the voids to seal the threads leaving most of the threads exposed to metal to metal contact. And the rods have always corroded as designed and never leaked.

[fj12ryder]

BB_TX wrote:
Seems even the "experts" are not in agreement. Some web sites have statements such as
Galvanic corrosion refers to corrosion damage that occurs when two different metals are in electrical contact in an electrolyte, where the more noble metal is protected and the more active metal tends to corrode.
Whereas some others have statements such as
This rapid corrosion occurred because of a chemical process called galvanic corrosion. Galvanic corrosion can only occur when two electrochemically different metals are close to one another and also submerged in an electrolytic liquid
Note the word "close" rather than "contact".
So I guess it all depends on which "expert" you are talking to at the time.

Not really, it all depends on the strength of the electrolytic liquid. As the boat guy said "The conductivity of the water is not adequate." And he is talking about salt water which is a much better electrolyte that the water in a water heater. So if you got a strong enough electrolytic fluid it should work without the two dissimilar metals being in physical contact.

[BB_TX]

Seems even the "experts" are not in agreement. Some web sites have statements such as
Galvanic corrosion refers to corrosion damage that occurs when two different metals are in electrical contact in an electrolyte, where the more noble metal is protected and the more active metal tends to corrode.
Whereas some others have statements such as
This rapid corrosion occurred because of a chemical process called galvanic corrosion. Galvanic corrosion can only occur when two electrochemically different metals are close to one another and also submerged in an electrolytic liquid
Note the word "close" rather than "contact".
So I guess it all depends on which "expert" you are talking to at the time.

[Cummins12V98]

MFL wrote:

bob213 wrote:
I believe it was Doug who suggested Rectorseal as the best alternative.

Yes he did, and while I've had no issue using tape, I'm going to give this product a try.

Jerry

ALL the Plumbers I worked with use RectorSeal. Some use Teflon Tape with some don't.

Most Teflon tape is junk, it's stiff. Like everything else there is junk look alike and there is quality.

[pigman1]

I don't know where the Suburban guy got his information and education about electrolysis, but he definitely needs to go back to school. fj12ryder has it absolutely correct. Corrosion is an electrical process and needs the anode in electrical contact with the metal being corrected. A simple test with an ohmmeter will tell you that the anode and the tank are in excellent electrical contact, even when teflon tape is used to seal the threads.

[fj12ryder]

donn0128 wrote:
No. According to Suburban the anode rod uses a chemical reaction NOT electrical.
It could be totally isolated from any metal and will still perform its intended function. Think sacrifical anodes on a boat for an example.

This had me wondering since I thought I knew how it worked, but you would think the Suburban assistant service manager might be aware, but according to this article from a boating magazine, he is incorrect.

"There is an unfortunate misconception that a sacrificial anode can be mounted anywhere, even hung over the side on a string, and it will still perform its appointed duty. That is dead wrong!

For a zinc anode to provide any protection, it must be in electrical contact with the metal being protected. The conductivity of the water is not adequate. We need low-resistance, metal-to-metal contact..."

He refers to zinc as that seems to be the material most commonly used on boats, but the operation is the same.

[twodownzero]

donn0128 wrote:
No. According to Suburban the anode rod uses a chemical reaction NOT electrical.
It could be totally isolated from any metal and will still perform its intended function. Think sacrifical anodes on a boat for an example.

Did you take chemistry in high school? Chemical reactions generally are electrical. I only took one semester so I can't say that all chemical reactions are electrical, but the ones I remember from class certainly were.

[ScottG]

I would rather use tape than sealant. The tape will come off cleanly where sealant is a lot more work to get comepletely off.

[DutchmenSport]

Delete

[MFL]

bob213 wrote:
I believe it was Doug who suggested Rectorseal as the best alternative.

Yes he did, and while I've had no issue using tape, I'm going to give this product a try.

Jerry

[BB_TX]

wgriswold wrote:
........
Do you have a reference for the Suburban statement. I can't find it on their site.
.......

The quoted statement in my post is from an e-mail from a Suburban assistant service manager when I ask if there needed to be electrical contact between the anode rod and the tank. The response came within a half day of my e-mailed question. Go to their web site, click on CONTACT US, and ask for further info if you need it.

"The answer is No. The metal threads do not need to make contact with each other. Electrolysis is the chemical reaction that takes place inside the tank and has nothing to do with the threads. I've attached some Suburban water heater videos to this email that I believe you'll find very interesting."

[bob213]

I believe it was Doug who suggested Rectorseal as the best alternative.

[donn0128]

Actually a guy posted a response from Suburban on another RV forum. Also based on wikipedia a maximum of three wraps of teflon tape is correct use. Like wiki explains the teflin tape once wrapped and the parts screwed together the teflon fills holes in the metal, but there is still plenty of surface for electrical contact.

Found this too
The role of the sacrificial anode rod

The anode rod is the most important factor in determining the life of your water heater. An anode rod is a steel core wire surrounded with one of three different metals. These metals include aluminum, magnesium, and zinc. The rod is screwed into the top of your water heater and protects your water heater from rusting. When the tank is filled with water the anode rod sacrifices itself to protect the exposed steel of the water heater, through a method called electrolysis. Electrolysis happens when there are two pieces of metal connected inside of water, the process makes the anode rod corrode in place of the exposed steel in your water heater. During this process the more noble (less reactive) metal will corrode over the less (more reactive) noble metal. Aluminum, magnesium, and zinc are all much less noble than steel, meaning they will corrode before the steel, which is why they are used for anode rods.

[wgriswold]

donn0128 wrote:
No. According to Suburban the anode rod uses a chemical reaction NOT electrical.
It could be totally isolated from any metal and will still perform its intended function. Think sacrifical anodes on a boat for an example.

The reaction is an oxidation/reduction reaction and involves the transfer of electrons from the anode to the cathode. Simply, oxygen is looking for electrons and finds them at the steel of the heater or the sacrificial anode which is then dissolved. There must be a way for electrons to flow from the sacrificial anode to the metal being protected.

On my boats the zincs were always screwed into the metal being protected, thereby allowing contact between the zinc and protected metal.

Do you have a reference for the Suburban statement. I can't find it on their site.

This is interesting, maybe I am wrong. If so I would like to figure it out.

Thanks.