Rusty microwave oven
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Why do microwave ovens rust and is it harmful? (Solved)

Microwave ovens provide one of the most convenient and quickest ways to cook food. However, like all cooking devices, they are prone to issues.

You might have looked into your microwave oven a few times before placing food inside and wondered, why is there rust in my oven?

Now in this article, we go straight into finding out why, if it’s harmful, and how to safely clean and prevent it in the future.

The question is, why do microwave ovens rust, and is it harmful to your health?

If you find rust inside your microwave, it’s likely due to spilled liquid from food that was left uncleaned. Generally, it’s not unusual that someone would clean their microwaves once a week, but with age and improper maintenance, rust can buildup. This can lead to safety and health risks.

In the following, we’ll discuss the origins such as why this happens, what health factors this can cause, and how to prevent it.

In order to understand the situation, let’s briefly go over where this rust comes from.

How does a microwave oven get rusty?

According to rust forms when metals corrode. The surface of the metal (often iron) will corrode first due to the presence of water and oxygen. And over time rust can and will entirely rust over becoming dust.

Dirty rusty microwave oven
Dirty rusty microwave oven

This process is very similar to a combustion reaction, like fire.

Oxygen is all around us so there’s no preventing that from getting into the microwave.

One variable that we can really control is the water part. This can actually be any liquid substance. Almost all liquid substances have a percentage of water in them.

Minor concentrations of water can also be found in solid foods as well.

If the old food or liquids are left and not cleaned, they will slowly react with the surface of the microwave and over time corrode the metal and turn it in to rust.

Are rusty microwave ovens dangerous to cook from?

There are many dangers to using a rusty microwave. Below are some of the most dangerous issues that can arise from a rusty microwave.

Rust in your food

Rusty microwave ovens can pose a poisoning threat to the food you cook.

Radiation is very bad for humans and living things and it certainly doesn’t help if you are heating your food along with the rust in the same closed container.

In contrary to how other websites are claiming that rust is not harmful to consume, I found this article from the U.S. Department of Agriculture. It states that

“Rust is not a food-safe material so it should not be ingested”


Sparks and fire

As rust forms inside the surface chamber of a microwave oven, it begins to eat into the paint of the oven. This exposes the metal underneath the paint.

Microwave ovens use radiation to cook food. Radiation comes in the form of waves and these waves are left to bounce throughout the inside of the microwave oven. When these waves have a frequency that doesn’t do well when it makes contact with bare metals.

If the wave hits the rust and exposed metal, you’ll see a spark occur. These waves bounce thousands and maybe even millions of times in a short period.

If enough sparks occur, you might be in danger of your microwave exploding or starting a fire.

Radiation leak

The paint that coats the inside of the microwave chamber not only protects the waves from sparks but also covers the non-metal, glass door as well.

A microwave chamber basically works as a Faraday cage. This is the kind of container that blocks EMPs and blocks your phone from getting a signal.

There’s a permeable layer of special conductive paint that covers the entire chamber including your glass door. If rust were to eat away at that paint, radiation can likely penetrate through the window and out to the external environment.

We’ve all peaked into our microwave ovens while it’s cooking our meals just to see the progress of the food. It’s not considered dangerous because the paint that covers the door keeps the radiation waves at bay.

Unfortunately, if that covering were rusted and eaten through, there would be little protection from the radiation waves and this can certainly cause harm to people and living things over time.

The proper way to remove rust from a microwave safely

When you’ve identified that rust has plagued the inside of your microwave, it’s time to start taking measures to remove it. You might even notice a layer of paint beginning to chip and peel around the outer edges of the rust. That’s another thing you’ll have to rectify.

Take these steps to make sure you properly get rid of the rust first.

  1. With a scraper or metal brush, gently scrape off the cracked and peeling paint.
  2. Brush gently until you no longer see any deformed areas of paint.
  3. Using a sander or any sanding surface, gently sand over the rusted area breaking and detaching the rust from the surface.
  4. Continue sanding until you find a smooth metallic surface.
  5. Repaint the surface with specialized ceramic paint.

Tips to prevent and properly maintain a microwave from getting rusty

Like all electronic devices and things in the house, if you don’t properly maintain and clean them, you’ll likely not be able to use them for long.

You have to properly maintain your microwave oven.

To keep it in good working condition, make sure to regularly scrub or wipe down the chamber with a dry cloth at least once a week.

Make sure the inner chamber is as dry as you can make it. Make sure there are no bits of food or liquid lingering in the microwave because as you now know, it will be the catalyst for rust to form.

There are actually a few neat tricks on how to prevent rust in a microwave. The following is a list.

  1. Place a container with lemon slices inside the microwave oven.
  2. Turn on the microwave and let it heat up the lemon water.
  3. Dry the entire microwave chamber with a soft, dry, non-abrasive cloth.

This acts as a cleaning agent that mistifies and spreads throughout the entire microwave. Be sure to gently wipe it all dry when done. Take care not to scratch any paint from the inside.

At what point must someone replace a microwave oven?

So it might be time to buy a new microwave. But what are the signs?

Watch out for these issues:

  • The buttons to operate the microwave no longer works.
  • The microwave door is broken and won’t shut.
  • Food is no longer cooking.
  • You smell something metal burning every time you use it.
  • It’s been more than 10 years plus any of the issues above.

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Final thoughts

Once in a while, make sure there’s no rust in your microwave.

Proper cleaning and maintenance will make your microwave lasting long and provide you with as many meals.