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Galvanic corrosion: what it is and how to fight it

Corrosion is the most common cause of malfunctions in heating systems. It is responsible for worsened heating efficiency, leaks, component failures and a shorter lifespan of the entire system. Find out how to effectively fight corrosion in your heating system.

Metal corrosion in heating systems

Why is corrosion so dangerous anyway? It destroys metal materials of heating systems and leads to a whole range of problems. At first it attacks and degrades the surface of those materials, but gradually it gets deeper and deeper, it can even create a crack or a hole in the heater or disrupt the connections. This results in a dangerous leakage of operating fluid.

Rust peels off and is released into the fluid. Rust particles clog the system, reducing the flow and heating performance and can destroy moving parts of the system.

There are several types of metal corrosion. In heating systems, you may encounter the following:

  • Oxygen corrosion: occurs when oxygen in the heating system reacts with metal (aerated radiators).
  • Galvanic corrosion: is an electrochemical phenomenon that results from the reaction of different metals that are connected by an electrically conductive solution.
  • Bacterial corrosion: is the result of the metabolism of microorganisms in the heating water.

What is galvanic corrosion?

Galvanic corrosion is also called bimetallic or electrolytic corrosion. Simply put, it is the formation of rust due to the interaction of different metals. Therefore, galvanic corrosion occurs provided that:

  • two or more different types of metals are connected by an electrically conductive solution (e.g. ordinary water, but moisture is often sufficient),
  • these metals have different corrosion potential and are not isolated.

Metals connected in this way are called a galvanic cell.

And how does galvanic corrosion take place? If the above conditions are met, one metal (the less noble one) becomes the anode and the other the cathode. The conductive solution then transfers electrons from the anode to the cathode, significantly accelerating corrosion of the anode. The cathode remains intact, or its corrosion is slowed in proportion to how the corrosion of the anode is accelerated.

Galvanic corrosion - the silent killer of heating systems.

Galvanic corrosion of metals in practice

In practice, this phenomenon can be encountered in heating systems that are made of several different metal materials. This is undesirable, a good designer should always think about galvanic corrosion and design the entire system, including all components, from single metal material without admixture, or from materials with the same or similar corrosion potential. If this is not possible, it is necessary to properly isolate the individual materials that could form a galvanic cell.

Even the boiler and other heating components can create a galvanic cell, it is also necessary to take into account their corrosion potential within the entire system.

How to get rid of rust

Rust is dangerous for two reasons:

  1. It disrupts the surface of materials, causing various leaks. Heating fluid may leak from the radiators and the overall lifespan of the heater is significantly shortened.
  2. Rust particles are released into the operating fluid and circulate in the heating system. Gradually, the heating and individual components become clogged, often leading to seizure of moving parts of the system (especially pumps) and other malfunctions.

You can prevent the negative consequences of corrosion processes by properly maintaining the heating system.

Prevention of corrosion

Prevention must correspond to the causes of different types of corrosion:

  • Prevention against oxygen corrosion simply by regularly venting the heating. Venting is also very important for optimal heating performance.
  • Galvanic corrosion is the result of an inappropriate combination of materials inn the system, in this case only a qualified designer and a quality heating design will help.
  • Microbial corrosion can be prevented by appropriate water disinfection before entering the system (if the water is pumped from a well or borehole).

Filtration of heating liquid

Using a magnetic filter, you can effectively and simply remove all loose rust particles from the liquid. Magnetic filters are already a part of modern heating systems, but their use is highly recommended even in older systems.

Caleffi filter and magnet drainer.

How does a magnetic filter for heating work?

Why are magnetic filters a necessity these days? Although modern heating systems are much less energy-demanding than older ones, they are also more complex. They usually consist of many parts and components, which results in the fact that several construction materials with different corrosion potential are used in them. As mentioned above, they easily create an unwanted galvanic cell.

In addition, pumps with a strong magnet are used in modern systems, which increases the pump's efficiency, but also catches magnetic metal fragments and sludge, which can lead to its worsened functioning or to seizing.

The solution to these problems is a magnetic filter for heating. This device very effectively removes all metals, metal sludge and rust from the operating fluid. It simply catches them using a strong magnet, which only needs to be cleaned about once a year. Since the magnetic heating filter works only on the basis of the laws of physics, its operation is 100% efficient, but it will be cost-free.