The case for sacrificial anodes in your cooling system

[tubman]

Originally Posted by corvette8n

Where’s the best place to get a chunk of magnesium?

I got mine from Amazon.com. Each piece yield 3 chunks. Here's a link : https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1.

[flatjack9]

Originally Posted by Floyd

You can get out your organic chemistry books and your studies of inorganic chemistry (a good review of them is always recommended), however this is a simple case of electrochemistry. (dig out that book and the periodic chart).
Boats use anodes for the simple reason that they live in salt water which is a terrific electrolyte and thus highly conductive. The boat sets up a great battery between the bronze propeller and the stainless shaft. The "zinc" i.e. anode is made from zinc in this case to be the anode in this battery, thus making both the prop and shaft cathodic .
In a car cooling system where you have complete control over the liquid, none of this is necessary. If you use distilled water and modern "coolant" and change it periodically like you do for brake fluid, say every two to three years, you will have the results just like Kube.
In the old days, distilled water was never mentioned for cooling systems. Combine that with basic "antifreeze" which was ethylene glycol and a bit of lubricants for the water pump only and you have a pending disaster. Tap water, well water or roadside pond water all have enough minerals and conductance and off PH to start a real electrical party. Old timy antifreeze had nothing to stop it.
Fast forward to 21st century (actually late 20th century) and we have well developed "coolants" that have explored removing phosphates and incorporating hybrid organic acids (controlled) for corrosion protection and a million other things. Combine this with distilled water and you have a perfect liquid system that is not a home made battery, thus the electro-chemical reaction remains at zero.
Use the new stuff and only distilled water. that is why it is rated for cast iron and alloy engines. The modern-modern cars take full advantage of this in having very specific coolants for their cars. i.e. G-05; G-12;G13 ;G-40 for German cars.
You can test your cooling system with a good VOM to see if you have a voltage (low-less than 0.5 volts being generated ) between the liquid and the block/radiator. This sometimes works. If you have any tap water or old "antifreeze" in the system, drain and flush immediately and refill with a modern hi quality coolant and distilled water.
You can then forget about it until the time to change it.

I like what Floyd has to say.

[tubman]

Originally Posted by flatjack9

I like what Floyd has to say.

In a perfect world, yes. However, conditions are different and can change. Who for example, has calculated the mix of materials (basically aluminum vs. iron) exposed to the coolant and determined the precise antifreeze product required for that particular combination? Nobody I know. As soon as the fresh coolant mixture has been in the engine one minute, changes are already taking place. Nothing takes the place of proper maintenance, but most people don't change their coolant once a year. For that matter, who do you know that changes their brake fluid every "two or three years" as mentioned in his post? Nobody I know. Perhaps those with a staff looking after their cars, but not most of us; this is a hobbyist forum, after all.

Look at the sacrificial anode as an indicator first and then as an insurance policy. In the first case, a casual inspection will give you an early indication if anything is starting to go wrong, and secondly, it's presence will serve as a partial cure if anything is going wrong. The anti-freeze mixture in my car was fresh 3 years ago in a clean engine. I didn't like what I saw, so a flush and refill is in order. The one thing I do know is the the material leached from the magnesium chunk did not come from the aluminum heads.

I fail to see why anyone would go to such lengths to avoid such an easy, effective method of checking and controlling cooling system performance.

[drolston]

This is the one from Mac's. the little wire wraps around the brass button at the bottom of the radiator cap and the chunk of zinc drops into the water when you put the cap on. Designed to protect aluminum. Mine has shown considerable erosion over five years, so it is doing something. Cheap insurance for the Offy heads.

https://www.amazon.com/MACs-Auto-Par...7674754&sr=8-4

[tubman]

As I have said before, the Galvanic Series table tells me that zinc is not the best anode to be used to protect aluminum. They are too close together. Magnesium is a better choice, which is why the RV's with aluminum water heater tanks use magnesium rather than zinc.

Zinc anodes are mainly for marine use, like "Floyd"'s example of a bronze propeller and a stainless steel shaft.

Look at the Galvanic Series table in both situations, and try to comprehend what it is telling you.

[Brian]

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Whilst a quick look at the periodic table will prove you correct tubman, my own experience using zinc anodes shows that they also work. I have experienced zero corrosion in my ali heads after about twenty years of using zinc anodes. I do change the anodes about every ten years or so, and they resemble swiss cheese.
I have made and fitted 'pencil' anodes into every 24 stud engine I've built over the years [I use 1/2 dia zinc rod, thread one end 1/4 pipe and using common 3/8 NPT plugs, I tap them 1/4 NPP, then screw the zinc pencil into the plug; it then sorta resembles a post 40 temp sender unit, these screw into the boss under the centre hose outlet]
My own personal engines are 37-38 blocks with the pump in heads fitted. This leaves theoriginal water pump openings in the block to be capped. Ford actually produced cast caps for this very purpose...I make my own out of 3/8 plate steel. The inside surface of these I tap to accomodate zinc 'rudder' anodes. These are big 'domed pancakes', just the right size to fit in the block openings, and provide a massive surface area with the coolant.
Irrespective as to whether you choose magnesium or zinc for your anode choice, the most important thing, that hasn't been mentioned, is that they MUST make a good ground. No use just dangling it into the top radiator tank on a bit of string!

[Crankster]

The "good ground" aspect is also a factor for the radiator itself, especially aluminum radiators. I'm not sure why this happens to aluminium in particular but stray voltage or current draw (as when starting the engine) or specifically electrical components "searching for a ground" can inadvertantly send serious amperage through the coolant and/or the radiator and eventually, ruin it. This damage or type of defect is not covered under warranty. The pictures I've seen of it show long dark vertical streaks externally, on the fins.