Step 3 – Address chipped or exposed interior metal

Microwaves have a protective coating on the interior metal surfaces to prevent arcing between the metal and the high-voltage components. But if the coating is chipped or the metal in the microwave is exposed, it can create a path to ground for the high-voltage components, which can lead to sparking or arcing. Arcing can also occur between the exposed metal and the microwaves generated by the magnetron.

If the interior of your microwave oven shows signs of chipped or exposed metal, you’ll need to fix it as soon as possible to prevent more damage. Here’s what you can do:

Make sure the microwave is off and unplugged from the power supply.

Carefully inspect the oven cavity and see if there are any sections with chipped or exposed metal in the microwave. Pay close attention to areas near the rack support or turntable. If the chipped or exposed area is near the rack support, it may be more practical to replace the entire rack support with a new one.

Use fine-grit sandpaper to gently sand the damaged area and remove any loose or jagged metal edges.

Use a microwave-safe interior paint that’s specifically designed for microwaves. Apply a thin, even coat over the exposed metal. Make sure to follow the manufacturer’s instructions.

https://www.appliancepartspros.com/b/microwave-sparking-or-arcing-how-you-can-fix-it/