Good Sam Club Open Roads Forum: Water heater, anode rod, electrolysis, and teflon tape
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 > Water heater, anode rod, electrolysis, and teflon tape

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fj12ryder

Platte City, MO

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Posted: 01/16/19 08:13am Link  |  Quote  |  Print  |  Notify Moderator

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.


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BB_TX

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Posted: 01/16/19 09:51am Link  |  Quote  |  Print  |  Notify Moderator

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.

* This post was edited 01/16/19 01:03pm by BB_TX *

fj12ryder

Platte City, MO

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Posted: 01/16/19 09:56am Link  |  Quote  |  Print  |  Notify Moderator

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.

memtb

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Posted: 01/16/19 01:23pm Link  |  Quote  |  Print  |  Notify Moderator

I have always used Teflon tape, my anode rod .......continues to “sacrifice” itself!


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Caesar Ritchie

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Posted: 04/15/21 05:43am Link  |  Quote  |  Print  |  Notify Moderator

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. To protect the metal of the water heater you need to take care while choosing the size of the water heater, there must be contact between the anode and the metal of the water heater.

BCSnob

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Posted: 04/15/21 06:47am Link  |  Quote  |  Print  |  Notify Moderator

Ions flow in the water between the heater metal and the anode rod; electrons must flow between the heater metal and anode rod via an electrical connection (at the threads) in order to balance the charge being produced during electrolysis.

If you disconnect one side of your battery from the RV (no electrical connection) do you get electrolysis inside your battery (do your lights work)?

Read up on Galvanic cells in:
Encyclopedia of Physical Science and Technology (Third Edition), 2003

* This post was edited 04/15/21 07:40am by BCSnob *

RKW

Four Corners, New Mexico

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Posted: 04/15/21 05:27pm Link  |  Quote  |  Print  |  Notify Moderator

The most convenient way found to change/monitor the anode rod was to join the threaded plug for the drain hole and the sacrificial anode in to a combo item. That's why the rod happens to be in close proximity to the threaded drain hole plug. The anode could have been located anywhere in the tank and still have worked well.

There is an electrical aspect to sacrificial anode that has nothing to do with threaded plugs. Because the anode is a different metal than the tank,there is a weak electric current in the water which is part of the process.


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  • fpresto

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    Posted: 04/15/21 06:39pm Link  |  Quote  |  Print  |  Notify Moderator

    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.

    While it may be often stated I have yet to see one that wasn't rapidly corrected. Everyone makes it too complicated. A voltmeter set to ohms will quickly prove that there is still continuity with the use of tape. you are dealing with microvolts so it takes very little contact.


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    lwbfl

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    Posted: 04/15/21 06:56pm Link  |  Quote  |  Print  |  Notify Moderator

    I use electrolysis to clean cast iron. There is no direct electrical connection between the two pieces (sacrificial metal and piece being cleaned) other than water. To make the process more efficient (which also rapidly increased the declining of the sacrificial metal or anodes)Sodium carbonate, Na2CO3, (also known as washing soda, soda ash and soda crystals) is added to the water. Both pieces are submersed in the solution, small positive charge attached to the anode, negative lead attached to the piece being cleaned. The piece being restored loses all organic materials and rust which gets transferred to the anodes. I suppose the point I'm trying to make with all of this is that no direct electrical connection is required for the chemical process other than the water.


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    BCSnob

    Middletown, MD

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    Posted: 04/15/21 07:09pm Link  |  Quote  |  Print  |  Notify Moderator

    lwbfl wrote:

    .....small positive charge attached to the anode, negative lead attached to the piece being cleaned.

    Doesn’t this simply provide the current (electrons) needed to balance the ion flow in the solution (in place of directly electrically connecting the two metal pieces) and help drive the desired electrochemical reaction?

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