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Old 03-21-2022, 10:50 PM   #21
Bill
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I wonder if a thin layer of anti-seize lubricant on the threads of a new anode rod would be a good idea? At least some anti-seize lubes are electrically conductive, so the electrical path needed for the anode rod function would be maintained. Does anyone have any experience with this?

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Old 03-22-2022, 07:42 AM   #22
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Default even Teflon tape (just one layer) has not created a conductivity "problem".

Interesting question from Bill.

I have been using 1/1-2 turns of non-conductive "Teflon Plumber's Tape" on my last few Rod changes, and those Anode Rods have still degraded appropriately. During installation, the threads are cutting through the tape, enough to support the miniscule "current" involved in the rusting process.

So I feel that a tiny amount of lubricant "anti-seize" on the Threads would have the same result - with no regard for whether the anti-seize is conductive or not, the heater's threads will cut against the rod's threads enough to provide adequate conductivity when the Rod has been tightened in.

I just hate the idea of putting a petroleum-based product on the Threads, causing a small amount to be squeezed towards exposure to the water upon tightening. Teflon tape is drinking water safe. In normal plumbing, I use at least 4 turns of tape before tightening threaded copper joints. But for this job, I use only 1-1/2: basically just one turn, plus enough to keep it from slipping while I thread the rod into the tank. So far, that minimal use has provided for 'good-enough' conductivity.

With a single layer of Teflon Tape preventing a lot of "grunge" from developing in the Threads, and doing a great job at lubricating the installation and subsequent removal, my last few anode rod changes have been super easy. (My first removal was very tough to accomplish, along the lines of the troubles described in this Thread).
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Old 03-22-2022, 08:54 AM   #23
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When pipe threaded items are screwed together there gaps between a lot of the threads as the male and female threads make contact and tighten in some areas. A small amount of water and air will fill the gaps in areas where no thread-to-thread contact is made. This starts corrosion and mineral deposits to fill those gaps. As steel corrodes, it expands causing the threads to tighten against themselves.

Teflon tape, anti-seize, and blue Loctite all achieve the same goal of filling those gaps with non-corrosive material that stays soft and aids in releasing the threads. This leaves no place for water and mineral intrusion, thereby, eliminating corrosion.

As for chemical intrusion from these preventative measures, I think it is a minimal issue with Teflon tape and properly cured Loctite. Anti-seize may or may not be a different issue. Personally, I never drink from the hot water faucet and our water filter is on the cold water side of the kitchen sink.
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Old 03-22-2022, 06:58 PM   #24
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Bill- What do you mean by the electrical path? The anode rod base doesn’t need to be conductive to the water heater.
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Old 03-22-2022, 09:35 PM   #25
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Quote:
The anode rod base doesn’t need to be conductive to the water heater.
Actually, I think it does. The chemistry of corrosion is fairly complex (at least to me), and is better explained by various electro-chemistry articles on the internet. And we have at least one knowledgeable chemist here on the Forum who may choose to explain it a lot better than I can. But the bottom line is that corrosion involves the flow of electrons (in other words, an electrical current). The way to prevent this flow of electrons is either to electrically insulate the iron from the water/oxygen, or to divert the flow away from the iron by giving it a more attractive metal to work with - aluminum, for instance - and let the aluminum corrode.

C'mon, let's have the chemist step up here, and rescue me.

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Old 03-23-2022, 11:58 AM   #26
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Wink Possibly not the particular chemist you had in mind - but here's my version..

With no anode rod, corrosion occurs on the water heater steel tank in a general way - it simply rusts, in the presence of water or air with humidity. The tendency to rust is different for different surrounding fluids, based on both the dissolved ions within the fluid (e.g. salt "Sodium +" and Chlorine -" ions in seawater). In tap water, the tendency to rust is also related to the acidity of the water (an imbalance of "Hydrogen +" and "OH -" ions within the water itself, and the fact that a water solution contains a significant proportion of split ions, rather than fully "connected" molecules.

The proportion of molecules in a split state is a function of temperature, and rusting speed increases a lot with higher temperatures.

Within a fluid, such as seawater (with lots of dissolved sodium choride, and much smaller amounts many other dissolved compounds as well), the tendency for one metal to corrode, in comparison to another, is indicated by difference of electric potential between two metal contacts exposed or submerged into the fluid and connected in a circuit outside. The metal with the LOWER potential will rust, typically accepting one or two OH- ions through the fluid. This rusting metal acts as the "Anode".

That process releases one or two electrons. In a completed circuit to the non-rusting "Cathode", the Cathode metal both receives and emits electrons - in electric current from the Cathode. Those are effectively used to create one or two new "HO-" ions at the fluid surface of the Cathode.

Neither metal maintains a net charge, but current flows in a circle. The electrons are "freed" at the rusting anode, flow in the non-fluid connection to the non-rusting anode, and then get passed from the anode back into the fluid. The critical non-fluid part of this circuit is between the threaded base of the anode rod and the threaded "cathode" tank rod sleeve, which must support a miniscule amount of electric current.

By providing a full circuit, using a sacrificial "Anode" rod which is MORE prone to rust, rust is prevented on the steel "Cathode" tank surface. In this table, the potential for rust versus other metals (in seawater) is shown in volts.

Metal Electrode potential, volt
Gold +0.42
Silver +0.19
Stainless steel (AISI 304), passive state +0.09
Copper +0.02
Tin -0.26
Stainless steel (AISI 304), active state -0.29
Lead -0.31
Steel -0.46
Cadmium -0.49
Aluminium -0.51
Galvanized steel -0.81
Zinc -0.86
Magnesium -1.36

When two different metals are given contact with the fluid, and a good conduction path is provided, the metal with the LOWER number will rust (as the "Anode"), and the metal with the higher number will be protected as the "Cathode".

Zinc (-.86) will be rusted, protecting the steel tank walls. You might note, if you're interested, that aluminum has a high tendency to rust. And it actually does that, in free air with humidity and especially with water exposure. But its rusted surface is nearly the same color, just a bit less bright than the bare metal - and it's held very tight to the surface of an aluminum bar or plate. Steel rust, in contrast, is held to the surface very loosely. It often flakes right off, and providing lots of little cracks for further entry of water to create rust further into the bare metal.

Galvanized steel bolts rust the zinc surface quite fast, but it is bonded tight to the steel and doesn't provide the holes and cracks for the underlying steel to rust very quickly (in moderately dry environments). There are also a few very specialized steel compounds, such as ASTM-A606-4, which hold the rust layer super tight, behaving more like aluminum. (People often refer to those products as "Cor-ten Steel", although that's the trademark name of a particular company, and even they no longer make in the original formula). They are meant to rust in a thin layer, and hold up many years - even in direct contact with sea water. But they're expensive, and not widely used.
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Old 03-23-2022, 05:54 PM   #27
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Well dip me in chocolate and call me a KitKat bar. I learned something new. I just thought it was because the anode material gave up electrons easier.
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Old 03-26-2022, 12:18 PM   #28
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Shane, Rick must be a chemist. Your answer sums up what Rick said in a Nutshe... I mean KitKat wrapper.

The reaction producing rust, most simply put, is:
4Fe + 3O2 -> 2Fe2O3

or more correctly, results from the balanced series of reactions:

4Fe + 3O2 + 6H2O ...-> 4Fe(OH)3
4Fe(OH)3 ................-> 4FeO(OH) + 4H2O
4FeO(OH) .............. -> 2Fe2O3 + 2H2O

If you look closely, the 4Fe(OH)3 and the 4FeO(OH) on each side "cancel" leaving you with the more simple equation equation I wrote above. But, the reaction cannot proceed without the presence of water because it is required in the intermediate steps.

As Rick stated, the metal with the LOWER electrical potential will give up its electrons easier. When Fe becomes Fe2O3 (rust), it has gone from Fe with no charge to Fe3+ because it lost 3 electrons overall. When iron (Fe) gives up its electrons in water according to the process above, that is rusting.

Just so you know, to understand the process completely, you need a grade 12 Chemistry course, and the electrochemistry unit is one of the hardest units in the course.

Tomorrow I will go over how to use the half-cell potentials to put together oxidation/reduction reactions in electrochemical cells, followed by electrolysis.
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Old 03-26-2022, 12:19 PM   #29
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Quote:
Originally Posted by Shane826 View Post
Well dip me in chocolate and call me a KitKat bar. I learned something new. I just thought it was because the anode material gave up electrons easier.
And don't Google it. You're smarter than that.
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Old 03-26-2022, 12:47 PM   #30
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Quote:
Originally Posted by Larryjb View Post
Shane, Rick must be a chemist. Your answer sums up what Rick said in a Nutshe... I mean KitKat wrapper.

The reaction producing rust, most simply put, is:
4Fe + 3O2 -> 2Fe2O3

or more correctly, results from the balanced series of reactions:

4Fe + 3O2 + 6H2O ...-> 4Fe(OH)3
4Fe(OH)3 ................-> 4FeO(OH) + 4H2O
4FeO(OH) .............. -> 2Fe2O3 + 2H2O

If you look closely, the 4Fe(OH)3 and the 4FeO(OH) on each side "cancel" leaving you with the more simple equation equation I wrote above. But, the reaction cannot proceed without the presence of water because it is required in the intermediate steps.

As Rick stated, the metal with the LOWER electrical potential will give up its electrons easier. When Fe becomes Fe2O3 (rust), it has gone from Fe with no charge to Fe3+ because it lost 3 electrons overall. When iron (Fe) gives up its electrons in water according to the process above, that is rusting.

Just so you know, to understand the process completely, you need a grade 12 Chemistry course, and the electrochemistry unit is one of the hardest units in the course.

Tomorrow I will go over how to use the half-cell potentials to put together oxidation/reduction reactions in electrochemical cells, followed by electrolysis.
Thanks for listing the intermediate reactions more concisely and completely. Don't ever let me answer a question about the reactions involved in different types of Lithium batteries, I'd go completely crazy discussing the various types of "doped" anodes.
I'll admit to having a bit of knowledge about redox reactions. However, most of my own 'professional-level' chemistry work, these days, involves the analysis and assessment of biologically "fermented" consumable liquids...
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