The Science Behind Corrosion in Closed Circuit Systems

Corrosion is a common problem in closed circuit systems that, if left unchecked, can lead to reduced efficiency, costly repairs, and even complete system failure. In this blog, we’ll explore the different types of corrosion, what causes them, and how you can prevent these issues to ensure your heating or cooling system runs smoothly for years to come.

Understanding Corrosion in Closed Circuit Systems

Corrosion is a natural process that occurs when metals react with their environment. In closed circuit systems, commonly used for commercial heating or cooling, corrosion can be particularly damaging if not properly managed. 

There are several types of corrosion that can occur, each with its own causes and effects.

Types of corrosion

1. General corrosion

General corrosion is the uniform wearing away of metal across a surface. This type of corrosion is predictable and tends to happen over time, which means you can catch it before it leads to major damage. However, if neglected, it can still cause issues like pipe thinning, which can weaken the system over time.

2. Pitting corrosion

Pitting corrosion is more aggressive and unpredictable. It occurs when small, localised spots on a metal surface corrode rapidly, often resulting in holes or cavities. Pitting is especially dangerous because it can quickly damage pipes or components without much warning.

3. Cavitation corrosion

Cavitation happens when small vapour bubbles form in a fluid and then collapse near a metal surface, causing damage. This can often occur in pumps where rapid pressure changes create these tiny, destructive bubbles. Cavitation can lead to reduced efficiency and damage to critical parts like pump impellers.

What Causes Corrosion in Closed Circuit Systems?

Corrosion can occur in closed circuit systems for various reasons, but some of the most common causes include:

Dissolved oxygen

Oxygen is one of the biggest culprits when it comes to corrosion in closed circuit systems. If oxygen finds its way into your system, it can accelerate the corrosion process, leading to rust and other problems. This can happen when systems are opened for maintenance, or if there are leaks.

In the Telephone House case study, Guardian Water Treatment found that oxygen ingress led to ongoing radiator leaks throughout the building. By using a real-time condition monitoring system, we were able to pinpoint low pressure points where oxygen was entering, causing significant issues with corrosion. 

Mixed metals

Using different metals in the same system can lead to galvanic corrosion. When two dissimilar metals are in contact in the presence of an electrolyte (such as water), one metal corrodes faster than the other. This type of corrosion can often be seen at connection points between different pipe materials (source).

Poor water quality

Water quality plays a massive role in the health of a closed-circuit system. Water that is too hard or contains high levels of chlorides can cause scale build-up or corrosive reactions. Hard water, for example, can lead to deposits of calcium carbonate that not only reduce efficiency but also encourage under-deposit corrosion.

Impact of Corrosion on System Performance

Corrosion doesn’t just damage pipes and fittings – it affects the entire system. Here are some ways in which corrosion can impact your closed-circuit system:

Efficiency losses

Corrosion deposits, like rust or scale, can build up inside pipes, reducing flow rates and blocking heat transfer. This can lead to reduced efficiency, higher energy bills, and even overheating of the system.

Corrosion can reduce system efficiency by up to 15% due to blockages and restricted flow. This can lead to increased energy consumption and significantly higher operational costs over time.

Increased maintenance costs

Corroded components need to be repaired or replaced more frequently, adding to maintenance costs. Regularly having to replace corroded parts also means more downtime for your heating or cooling system, which can be disruptive to operations.

In the Telephone House example, using real-time monitoring allowed Guardian Water Treatment to identify and fix issues before significant corrosion took hold. This proactive approach saved the client from costly repairs and operational downtime.

Safety risks

If corrosion is not managed, it can lead to system failure, which could pose safety risks, especially if your heating system is responsible for temperature control in critical environments.

Preventing Corrosion in Closed Circuit Systems

1. Use corrosion inhibitors

Corrosion inhibitors are chemicals that help prevent corrosion by forming a protective layer on metal surfaces. Choosing the right inhibitor is crucial – for instance, azoles are excellent for copper, while phosphates work well for iron-based metals.

2. Maintain water quality

Monitoring and maintaining water quality is one of the best ways to prevent corrosion. Using demineralised or deionised water helps reduce the number of corrosive elements in the system. Regular checks on pH levels and hardness are also key – keeping the pH balanced will prevent metals like aluminium from corroding.

3. Real-time monitoring

Installing a real-time monitoring system can help identify potential issues before they become major problems. In the Telephone House case study, real-time monitoring allowed for early detection of pressure issues, which helped stabilise oxygen levels and prevent further corrosion.

FAQs about corrosion in closed circuit systems

What are the common types of corrosion in closed circuit systems?

The most common types of corrosion are general corrosion, pitting corrosion, and cavitation corrosion. Each type has different causes and impacts on system health.

How can I prevent oxygen from entering my system?

To prevent oxygen ingress, make sure your system is properly sealed during maintenance and ensure pressure is stable. Using real-time monitoring can also help identify and resolve pressure issues that may be letting oxygen in.

Why is water quality important in preventing corrosion?

Water quality affects the chemical reactions that can take place within your system. Hard water, for instance, can lead to scale build-up, while water with high chloride levels can increase the risk of pitting corrosion. Using demineralised water and regularly testing for pH and other chemical properties can help prevent these issues.

What is galvanic corrosion and how can I prevent it?

Galvanic corrosion occurs when two dissimilar metals are in contact in an electrolyte, leading to accelerated corrosion of one of the metals. To prevent it, avoid using incompatible metals in your system or use electrical isolation between them.

How does real-time monitoring help in corrosion prevention?

Real-time monitoring allows you to track key system parameters like pressure, pH, and oxygen levels continuously. By doing so, you can catch any signs of corrosion early, allowing for timely corrective actions before serious damage occurs.

Conclusion

Corrosion in closed circuit systems is a serious issue that can lead to reduced efficiency, increased costs, and even system failure if not properly managed. By understanding the types of corrosion and their causes, you can take proactive steps to prevent them. Using corrosion inhibitors, maintaining proper water quality, and implementing real-time monitoring are some of the most effective strategies to keep your system healthy and running smoothly.

If you want to learn more about how real-time monitoring can help prevent corrosion in your system, read our Telephone House case study here.