This video and article look at the pros and cons of an “aluminium vs magnesium anode rod”
Water heaters typically come with magnesium or aluminium anodes. We prefer magnesium.
We dislike aluminium for 8 reasons. Those are:
First off, aluminium, being lower on the Galvanic Scale than magnesium, produces less driving current between anode and cathode (in this case, the tank is the cathode). We think that means it doesn’t do as good a job of protecting the tank, especially in softer waters.
Second, it produces about a thousand times its original volume in corrosion byproduct, most of which falls into the bottom of the tank as a sort of jelly, and adds to sediment buildup there.
Third, that gunk also occasionally floats out the hot-water port, appearing as a cottage cheese-like substance clogging tap aerators and water filters.
Fourth, the rod actually expands as it corrodes so that it is hard, or maybe impossible to remove one a few months after installation because its diameter is bigger than when it was installed.
Fifth, along with that, it has a tendency to split off from the core wire. So that chunks fall into the bottom of the water heater, where they stop being anode and start being junk. That also means that if you try to take one out at that point, it may split away from the core wire and snag the underside of the top of the tank, like a fish hook.
Sixth, the build-up of sediment on the bottom of gas heaters encourages noisy operation. Some people can hear their water heaters loud and clear at night, which is not helpful for those wishing to sleep.
Seventh, There is a little booklet “The Danger of Food Contamination by Aluminium” by Dr. R.M. Le Hunte Cooper. It details the nasty things aluminium does to the body. The liver, brain, kidneys and spleen seem to be the main repositories. With nervous tissues holding the most by weight. It was written in 1932. Modern plumbing allows some water that came from the heater to be used as cold water / drinking water. This doesn’t matter if magnesium is used in the heater.
Eighth. If you find yourself ground zero in a disaster, and the water main is broken, about the last thing you want is to be drinking heavily-aluminium-laden water from the bottom of your water heater. The source of last resort. It could make you sick in dreadful ways: trash your stomach and intestines, create instant arthritis in your joints. Not good!
What are the exceptions to the rule?
The only time aluminium anode rods may make sense is in very hard water areas. In these areas a magnesium anode may be used up so fast that its simply not practical. In this case it would be wise to use a good quality water filter to make sure you don’t ingest any aluminium.
Who wins the great aluminium vs magnesium anode rod debate?
So in conclusion, when it comes to the debate of an aluminium vs magnesium anode rod, in most cases, a magnesium anode rod is the best choice for your hot water system.