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Can a Furnace Corrode?


If you’re asking this question and looking for answers online, it’s probably because you think you’ve found corrosion on your gas furnace. Or perhaps you’re curious because you have an older furnace and you want to know what can happen to it as it ages. Whatever the reason, we’re glad you asked because corrosion is an important topic when it comes to furnaces.

So the simple answer is, Yes, a gas furnace can corrode. It’s not something you want to happen, and it’s often a warning that the furnace needs to be replaced.

How Corrosion Occurs in a Furnace

When people think of corrosion, they usually think of rust first, which is one of the most common types of corrosion. But because people think rust only occurs when water comes in contact with metal, they assume it can’t happen in a gas furnace. A gas furnace doesn’t use water to heat the air, so how could it corrode?

A gas furnace may not circulate water, but it does create water vapor during its combustion process. As the combustion gases in the heat exchanger cool down during the heating cycle, they turn into a vapor that contains water moisture. There are other vapor chemicals that can also lead to corrosion. 

Most of this moisture escapes out of the exchanger through the flue. However, corrosion may form when metal in the heat exchanger is exposed to these vapors, Corrosion can also appear in the flue or other places where exhaust vapors move.

If the furnace isn’t venting properly, the process of corrosion will speed up. You may have a furnace that safely removes toxic gases but still allows too much combustion vapor to remain in the exchanger. 

Leaks from the air conditioning system can also cause corrosion. In most HVAC setups, the AC unit is located over the furnace. If condensate moisture begins to leak from the air conditioner because of a malfunction, it will drip down onto the furnace and lead to corrosion.

Why Corrosion Is a Serious Problem

You don’t want corrosion on a gas furnace because it weakens the metal and combustion gases can escape from the heat exchanger. This is a major danger because it releases toxic gases such as carbon monoxide into the air that is blown into the house. Cracks in a furnace’s heat exchanger require immediate attention. Either the heat exchanger or the entire furnace must be replaced. If the furnace is older than 15 years, it’s best to have a new furnace installed. 

The best way to prevent corrosion from getting an early hold on your furnace is to always have professional maintenance for it each year. Our technicians will carefully inspect the unit for indications of corrosion and ensure the furnace is venting properly. 

If you notice corrosion anywhere on your gas furnace, you should stop using it and call us for help with your heating in Parker, CO

Rely on the experts at Peak Home Performance when you have concerns about your furnace. Guaranteed Comfort and Affordability.

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