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Aluminum vs Magnesium Anode Rod: What’s the real difference?

Aluminum and magnesium anode rods are more reactive than water heater metal. Magnesium is more reactive than aluminum. Thus aluminum is good for hard water. Magnesium is good for soft water to keep up with the many corrosive elements. But, magnesium rods do not last as long and need more frequent replacement.

Difference Between Aluminum and Magnesium Anode Rods: Overview

Both aluminum and magnesium anode rods provide the function of preventing your water heater from becoming rusted and corroded. Their specific properties help them attract the reactive elements from the water that cause corrosion, and the rod itself becomes corroded as opposed to the actual tank.

Their most distinguishing difference comes from how they function. Where aluminum rods are much slower at doing their jobs, magnesium ones are a lot more reactive and therefore perform a lot faster to attract the corrosive elements.

Another important difference is that magnesium rods actually provide certain health benefits to the user, as magnesium is super important for a variety of bodily processes. Aluminum rods, on the other hand, do not do this.

Aluminum Anode Rods

Relevant Characteristics of Aluminum

Aluminum makes a wonderful material for the manufacturing of anode rods as its characteristics are perfect for its function.

Aluminum is more reactive to corrosive materials than steel (what water heater tanks are typically made from), which means anode rods made of this material will preferentially corrode once it has come into contact with corrosive elements in the water.

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Aluminum also has a high reactivity to hot water, which makes it suitable for use in a water heater tank as once the water has heated, the anode rod will perform faster and more efficiently.

Design of Aluminum Anode Rods

Aluminum anode rods are widely used because of their specific design. For instance, this metal is extremely light and capable of bending quite easily. This flexibility makes it easier to manufacture and install, and its light weight means it is easy and cost-effective to transport.

The metal’s flexibility allows for customized rods to be made to suit all shapes and sizes of water heater tanks.

Some anode rods are not entirely comprised of aluminum. You can get the option of purchasing an aluminum/zinc combination rod, which has majority aluminum, a small percentage of zinc, and then an even smaller percentage of trace metals. The combination of these metals provides the benefit of reducing odors from your water tank.

Ability to Handle Hard Water

These types of rods are best suited for water that has a higher pH level and is generally quite hard. Aluminum rods withstand harder water a lot better than rods made of other metals. Since aluminum rods are less reactive than magnesium, they find the balance between lasting longer in water and still preferentially corroding instead of the tank. However, this is only applicable when there are moderate amounts of corrosive elements.

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Average Lifespan of Anode Rod

Depending on just how hard your water is and the overall quality of it, your anode rod will last you a maximum of 5 years. If you have generally hard water, and therefore have to make use of a water softener, then your anode rod will have a shorter life span as the softener will increase the corrosion of the rod.

Too much water softening can reduce the lifespan of the rod to less than a year!

You will be able to determine when it is time to replace your anode rod when the inner tubing becomes quite exposed; a few holes are normal and indicative that the rod is performing well, but when a large portion of the inside cable becomes visible, you are at risk of damage to the tank of your water heater.

Cost of Aluminum Rods

Aluminum rods are often the first choice for people as they are the lowest-priced metal rods of the options available. Aluminum is the most widespread metal on the planet, so the abundance of availability makes them super affordable.

You can find one of these rods for around $15, and they are readily available to purchase from most home-good stores and even online.

Health Benefits of Aluminum

While magnesium does provide people with a variety of health benefits as you will read further down, aluminum itself is known to be important in the food preservation process and has even been used in the formation of medications and vaccines.

Aluminum sulfates that are found in water assist in the water purification process.

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Magnesium Anode Rods

Relevant Characteristics of Magnesium

Magnesium is a suitable metal to use for the manufacturing of an anode rod as it has certain characteristics that assist in the process of sacrificial corrosion.

Magnesium is highly reactive to corrosive elements, more than steel and more than aluminum, which makes it really suitable for its function on an anode rod.

Magnesium also releases more electrons than aluminum does, which is why it works so effectively as the electrons are needed for the electrochemical process to occur to allow for the corrosion to take place on the rod and not on the water heater itself.

Design of Magnesium Anode Rods

Magnesium anode rods are generally quite light, making them convenient to transport.

These rods are not usually just made of one metal but are also comprised of other trace metals, although the main metal portion is magnesium.

Ability to Handle Hard Water

Unlike aluminum rods, magnesium anode rods should not be placed in water heaters that receive hard water. Magnesium rods are unable to withstand the number of minerals in the water, and the corrosion process will be accelerated significantly.

Your anode rod will then become covered in limescale or corroded to the point where it can no longer function efficiently, and if left unreplaced for too long, will cause your water heater tank to become rusted quite quickly.

However, this very feature is what makes magnesium anode rods better equipped for soft water. Soft water contains high numbers of corrosive elements—too many for the less reactive aluminum rod to keep up with. The magnesium rods are so reactive that they will be able to keep up with these large amounts of corrosive elements. This has durability repercussions as you can imagine.

Average Lifespan of Anode Rod

Despite its benefits, magnesium anode rods tend to last for a shorter period of time than aluminum rods.

The difference is not too significant as research shows that these rods can also last up to 5 years, but it all depends on the quality of the water that runs through your water heater. It is common for one to have to replace their magnesium rod after just 12 months.

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Water with a lot of minerals or that is very hard, will cause the anode rod to corrode a lot faster than better quality water. Magnesium rods are less durable when it comes to hard water, so the same amount of hard water that will take a few years to corrode an aluminum rod will take significantly less time to corrode a magnesium anode rod.

Cost of Magnesium Rods

Magnesium rods are not as cheap as aluminum rods, but they won’t necessarily break the bank either. Depending on the size of your water heater, and therefore the required size of the anode rod, you can expect to pay a minimum of $30 for a magnesium anode rod.

Health Benefits

Magnesium anode rods are sometimes chosen as they have the added pro of providing the user with health benefits. Research has shown that magnesium is important for providing humans with energy, assisting in the production of protein in the body as well as in the movement of muscles.

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Adding magnesium to the water via the anode rod allows the human body to function optimally as this nutrient is vital for a number of chemical processes.

Table of Differences Between Aluminum and Magnesium Rods

Aluminum Anode RodsMagnesium Anode Rods
Better suited for hard waterBetter suited for soft water
Has a longer lifespan as it takes longer to corrodeWill not last as long as an aluminum rod as corrosion occurs faster
More affordable than a magnesium rodMore expensive than aluminum rods
Does not provide any other benefits to the userThe dissolved magnesium in the water can provide the user with a variety of health benefits.

Should I Use an Aluminium or Magnesium Anode Rod?

The choice of which anode rod you should use comes down ultimately to the type of water that flows through your house.

Aluminum anode rods are better suited for houses that suffer from hard water, whereas magnesium anode rods work best in softer or softened water. However, if you live in an area where your water is not that hard nor that soft, then the choice is yours.

Your decision can be made based on your budget and how long you are willing to wait before needing to replace the anode rod.

If you are struggling with smelly well water, then neither magnesium nor aluminum anode rods is going to be your best choice. Rather go for a zinc alloy rod.

Of course, you could always go with a water heater that does not need an anode rod; not all of them do.


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