Microwave cavity rusting, with paint peeling or rust spots visible inside.

Safety note: Small rust spots can often be repaired; extensive corrosion near the waveguide or door seal may render the microwave unsafe.

Step-by-step checks:

• 1. Clean and dry: Thoroughly clean the cavity and dry it. Identify all rusted or peeling areas.
• 2. Sand and treat small spots: Lightly sand small rust spots to remove loose material. Wipe clean.
• 3. Apply microwave-safe cavity paint: Use only high-temperature, microwave-safe cavity paint to touch up bare metal. Follow the product instructions and allow full curing time before use.
• 4. Evaluate severity: If rust is extensive, especially around the waveguide cover or door seal area, discontinue use and consult a technician. Structural damage may not be repairable safely.