Is oxygen responsible for boiler corrosion

The heater is rusting - what you can do against corrosion

In addition to stone formation, plumbers and system operators are often confronted with corrosion of the heating system. This is a problem because the result of corrosion is decomposed metal. How does this happen and how can it be avoided? Learn more.

What is corrosion and what consequences does it have for the heating system?

When metal reacts chemically with substances from its environment and a new substance is created, one speaks of corrosion. When materials corrode, their original texture or surface changes.

In practice, a distinction is made between dry and wet corrosion. Dry corrosion is caused by the action of gases on metals, e.g. from exhaust gases. Wet corrosion develops through the migration of ions from the original material, through the action of moisture.

Wet corrosion predominantly plays a decisive role in heating systems. Corrosion then means that the heater will rust. The rust in pipes, on radiators or the boiler is caused by the reaction of iron under the action of moisture with oxygen.

The corrosion of boilers and the like can also be promoted by exhaust gases, humidity or the nature of the heating water.

What exactly happens when there is corrosion in the heating system?

Corrosion - i.e. rust - occurs in heating pipes as a result of the reaction of oxygen in the air with metal. If the oxygen is consumed by the chemical processes, hematite or magnetite can form, which is deposited in the pipe. The expert also speaks of "black sludge". This sludge can move through the heating circuit and thereby clog pipes, pumps or valves. The consequence of a corroded heating system can ultimately lead to total failure.

If existing rust spots are not remedied in good time, increased corrosion can occur. Then the rust spreads like a virus in the entire pipeline system, settles and “eats” its way through the pipes. Many a car owner of an older car is certainly familiar with the problem of "rust corrosion". The situation is similar with corrosion in the heating system.

Types of corrosion on heating systems

  • Corrosion caused by oxygen: This form of corrosion is also known as “pitting”. It occurs when too much oxygen circulates in the heating circuit. The oxygen can react with the metal, especially in places where the heating water is only moved slightly.

Remedy: Do not refill the heater too often; Bleeding after filling; Use of diffusion-tight pipes.

  • Corrosion during standstill: If a heating system is not used for a long time, standstill promotes corrosion. This is especially true if the heating water has not been sufficiently degassed or the water is too acidic.

Remedy:Ventilation of the heater before long periods of standstill; Use of alkaline heating water; regular control of the pH value.

  • Crevice corrosion: In this case, it is not the pipe material that corrodes, but the hemp sealing material.

Remedy: Pressing or welding pipes

  • Corrosion due to erosion: If the heating water flows too quickly through the pipes at high operating temperatures, the surface can be eroded in continuous operation and promote corrosion.

Remedy: Setting the correct performance pressure; hydraulic balancing

  • Corrosion due to halogens: If laundry is dried in the room where the heating system is installed or cleaning agents are frequently used there, chlorine and fluorine compounds from the air can settle on the boiler or thermal bath through condensation and cause corrosion.

Remedy: No laundry drying in the boiler room; No storage or excessive use of cleaning agents in the heating installation room

Corrosion prevention with the right heating water

The quality of the heating water has a major influence on the corrosion of a heating system. Therefore, when planning the heating, it should be taken into account how acidic or basic the water is. If the water is too hard, softening or partial softening of the heating water can be useful.

As a rule, the pH of the heating water should be between 8 and 10.5. Then the water is slightly alkaline and attacks metal surfaces less. With closed heating systems, the oxygen content in the heating water should be less than 0.1 milligrams per liter.

When radiators rust

Radiators can also rust. The rust attack can be promoted by different causes. Radiators in the bathroom or kitchen are particularly affected, i.e. in places where the humidity is usually higher than in other rooms.

Other causes of rust on radiators:

  • the material quality is poor
  • the paint layer is too thin
  • no professional cleaning
  • Damage to the paint surface
  • insufficient ventilation of the rooms
  • too high humidity in the room
  • Use for drying laundry

To prevent rust on radiators, you should avoid high humidity in the room and repair any damage or rust spots quickly. Because, as mentioned, rust can quickly spread over the heating pipe system and also appear in other places. Small rust spots can be remedied by a new coat of paint after the rust spot has been sanded off.

Conclusion: With regular heating maintenance you can reliably identify and repair corrosion damage

The most important step in combating corrosion on the heating system is regular maintenance. Your heating contractor can check for rust or other corrosion spots during each maintenance, determine the pH value of the heating water and top up the heating water correctly.

In addition, heating maintenance ensures that your heating system is functioning at the optimal flow rate and pressure. It is advisable to have your heating system checked at least once a year.

By the way, it is also important that you actually use your heating system in winter. In this way you avoid, among other things, that condensation water settles on radiators and can promote corrosion there. It is also ensured that the heating circuit does not come to a standstill.