Boiler Corrosion Causes, Effects & Prevention

James Elston
Written by James Elston
Updated on 17th May 2024
Posted on 16th May 2024
Topic: Boiler Advice
Boiler Corrosion Causes, Effects & Prevention

Boilers and heating systems are essential for preserving cosy living conditions during the winter months. On the other hand, corrosion poses a serious risk to the effective operation and longevity of these systems.

A chemical reaction or process between metal parts and the environment, known as corrosion, causes the metal parts to deteriorate and eventually fail.

The causes, signs, treatments, and prevention of corrosion in heating systems will all be covered in this expert guide.

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What Leads To Boiler and Heating System Corrosion?

The reaction of metal surfaces with oxygen and water causes corrosion in heating systems. The air’s oxygen mixes with the oxygen on the metal surface to cause oxidation. 

By moving ions between the metal surfaces, water functions as an electrolyte to quicken the chemical reaction. Moreover, the presence of contaminants in the water, extreme pH levels, and high temperatures can all contribute to corrosion.

What are the Signs of Corrosion in a Heating System?

The signs of corrosion in a heating system can vary, depending on the severity and location of the damage. Common signs include rust-coloured water, leaks, noises, reduced heat output, and foul odours. These symptoms should not be ignored as they can lead to system failure, higher energy bills, and health hazards.

How Can Heating System Corrosion Be Prevented?

The following preventive steps, among others, are the best method to avoid corrosion in heating systems and are particularly important if you are looking for a gas boiler replacement.

  • Use corrosion inhibitors: Chemicals that can be added to water to lessen the chemical reactions that cause corrosion are known as central heating inhibitors. They can be integrated into new systems or applied during system installation.
  • Frequently Flush the System: By routinely flushing the heating system, corrosion can be avoided by removing accumulated sediments, sludge, and debris. Annual flushing is advised, or as instructed by the manufacturer.
  • Managing Water Quality: Corrosion risk can be decreased by ensuring that the water quality satisfies the manufacturer’s requirements. The use of water treatment systems or the addition of chemicals to the water can accomplish this.
  • Install safety precautions: Important heating system components can be shielded from corrosion by installing safeguards like sacrificial anodes.

What are the Common Types of Inhibitors Used in Heating Systems?

There are various kinds of corrosion inhibitors for central heating systems, including:

  • Phosphates: Used to stop corrosion brought on by oxygen and scale formation.
  • Silicates: Used to maintain the pH of the water and prevent corrosion brought on by low pH levels.
  • Organic Inhibitors: Used to stop corrosion brought on by oxygen and other water contaminants.

How frequently should your heating system be flushed to avoid corrosion?

Your heating system’s kind and water quality determine how frequently you should flush it. It is generally advised to flush the system once a year or as directed by the manufacturer.

Read more about power flushes here

What material prevents corrosion the best when used for radiators and pipes?

Because they are resistant to corrosion, copper and stainless steel make the best materials for pipes and radiators. They are more expensive than other materials though, including cast iron or galvanised steel.

Can corrosion lead to the failure of a heating system?

Certainly, corrosion can lead to the failure of a heating system. Leaks decreased heat production, and eventual failure can result from corrosion weakening the metal components.

How much does it cost to fix a corroded heating system?

Depending on the type of heating system and the amount of damage, corroded heating system repairs might be expensive. Small fixes can run you a few hundred bucks, but big fixes or replacements can run you thousands.

What Will Help Control Corrosion In A Heating System?

Regular maintenance and the use of corrosion inhibitors can help control corrosion in a heating system. Regular maintenance includes flushing the system, inspecting the components for signs of corrosion, and addressing any issues promptly. 

Adding corrosion inhibitors to the system can also help prevent corrosion by reducing the chemical reactions that cause it. Corrosion can also be managed by taking additional safety precautions like setting up sacrificial anodes or utilising water treatment systems.

Why Is Hot Water Worse Than Cold For Corrosion?

Since the pace of chemical interactions between metal surfaces and water is accelerated by the greater temperature, hot water is more corrosive than cold water. The corrosion process is accelerated further by the increased acidity of the water brought on by the greater temperature. As a result, it’s critical to confirm that the water quality complies with the manufacturer’s requirements and to use corrosion inhibitors to guard against system damage.

How Can A Boiler Be Prevented From Corroding?

Preventive steps must be taken in order to stop a boiler from corroding, such as:

  • Regular system flushing is necessary to get rid of accumulated sediments and debris.
  • Using corrosion inhibitors to reduce the chemical reactions that cause corrosion.
  • Installing a magnetic filter to remove magnetite and other metallic debris from the water.
  • Maintaining the proper water chemistry, such as pH levels and hardness, to prevent corrosion.

Read all about magnetic filters here

How Long Should A Radiator Last Before It Rusts?

The lifespan of a radiator can vary, depending on the material, quality, and maintenance. Copper and stainless steel radiators can last up to 50 years or more, while cast iron radiators can last up to 100 years with proper maintenance. However, if the radiator is not maintained correctly, it can rust and fail much sooner.

Read more about the best radiators here

Can You Fix A Corroded Radiator?

Depending on the damage’s severity, a corroded radiator can be repaired. While minor corrosion can be treated by washing and repainting the harmed sections, substantial corrosion may need replacing the radiator or some parts of it. It is important to address any corrosion symptoms right once to stop the system from suffering any harm.


In conclusion, corrosion is a significant threat to the efficient operation and lifespan of boilers and heating systems. Preventive measures, such as using corrosion inhibitors, flushing the system regularly, and maintaining proper water chemistry, can help control corrosion.

Installing protective measures, such as sacrificial anodes, can also prevent corrosion from affecting critical components of the system. Regular maintenance and addressing any signs of corrosion promptly can help extend the life of the heating system and prevent costly repairs or replacements.

Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 16th May 2024
Topic: Boiler Advice

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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