Furnace Corrosion: Yes, It Does Happen

furnace-repair-technicianWhen you think of parts of your home that might suffer from corrosion, is your gas furnace one of them? Probably not. Corrosion is something people connect with water meeting metal. Parts of the kitchen sink may corrode, a water heater might corrode, but you don’t expect a furnace to have this problem. A furnace doesn’t use water, after all.

But, as this blog post title can tell you, corrosion can occur with a gas furnace. In fact, it’s common in older furnaces and often a sign that a system needs to be replaced. Should you see rust or other kinds of corrosion affecting any part of your furnace, we urge you to call for professional HVAC technicians to find out what’s happening and what can be done to ensure you have a working furnace for the rest of the winter.

Why a furnace corrodes in the first place

Corrosion doesn’t need liquid water against metal to happen. This chemical reaction can occur from contact between the combustion gases in the furnace and the metal walls. A furnace is designed so the combustion gases are rapidly vented away from the furnace’s heat exchanger and out a flue. This way the vapor in the combustion gas doesn’t have time to form along the heat exchanger walls and cause corrosion. Eventually—usually after a furnace has been in service for 15 years or more—the exposure to the vapor from the gas will allow corrosion to start. It may take hold earlier if the furnace is venting poorly.

Another possible cause is water dripping from the air conditioner above the furnace. This is less common, and it’s a repair that needs to be done to the air conditioning system. Never hesitate to have the AC fixed if you notice water leaking from it down onto the furnace.

The problem with a corroding furnace

What’s the big deal with some rust on the furnace? Aside from a warning sign that the furnace is getting too old for its job, corrosion poses a potential major hazard that can lead to carbon monoxide leaks. Corrosion weakens metal, and it’s likely to start on the heat exchanger in a furnace since this is the spot where the combustion gas collects. If the corrosion eats through the metal of the heat exchanger, the exchanger may start to crack. The combustion gases in the heat exchanger will escape through the cracks and right into the air heading into the home. This is dangerous! If you notice corrosion anywhere on your furnace, it may mean it’s affecting the heat exchanger. Although the heat exchanger can be replaced, it’s often more cost effective to scrap the old furnace and get a new one.

If you have corrosion on your gas furnace, contact us for furnace repair in Albany, OR. We’ll take a close look at the system and give you an honest assessment about whether we can fix it to keep it going for another few years, or if you need to arrange for a furnace replacement with us.

Midway Mechanical Inc. has served the Willamette Valley for more than 40 years.

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