The case for sacrificial anodes in your cooling system

[tubman]

Originally Posted by Kube

Tubman, I have to wonder what else might be going on in your cooling system.
I'd installed NOS heads on my '36 roadster about two years ago. At that time, I'd installed a diode in the same fashion as you.
Because of your post, I'd inspected mine and found it to be nearly as new. I had to look very closely to see any type of corrasion upon it.

To be clear, it's an anode. Do you remember what your anode was made of? It makes a difference. Magnesium is the least "noble" metal there is (see the attached "Galvanic Series" chart). If yours was zinc, it wouldn't have worked nearly as well as the magnesium chunk. If you look at the chart, aluminum alloys and zinc almost overlap at -1. I also put one in the brand new fresh "Hot Rod" engine I am putting in the "Tub" I am building. Everything in that engine is new. I had tap water and "No-Rosion" in it last summer for a couple of weeks and then drained it when I went to Florida for the winter. That anode also had noticeable corrosion on it (I checked it when I saw what was going on with my '51).

As to the NOS aluminum heads on your roadster, unless you know what material your diode was, you might be better of checking the heads for erosion, rather than the anode. I have seen aluminum anodes (which work if there is no other aluminum present) used to protect iron and steel.