Yes, it can be dangerous to put a sheet pan with rust on it in the dishwasher. Rust is the result of the oxidation of metal, and when it comes into contact with water, it can accelerate the corrosion process. Here are some potential issues to consider:
Spread of rust: The rust on the sheet pan can flake off during the dishwasher cycle, and the rust particles might end up on other dishes, utensils, or the dishwasher's interior. This could potentially contaminate your other items and lead to rust stains on them.
Damage to the dishwasher: The rust particles may not only affect your dishes but could also harm the dishwasher's internal components, such as the spray arm, pump, or filters. Rust can cause blockages or damage to these parts, affecting the dishwasher's performance and potentially leading to costly repairs.
Food safety concerns: If the rust particles mix with the water and come into contact with your dishes, it might be ingested with your food. While small amounts of rust are not usually harmful, it's best to avoid any unnecessary ingestion of rust particles, especially if you have any allergies or sensitivities to metal.
To avoid these potential issues, it's better to hand wash the sheet pan with rust on it using warm soapy water and a scrubbing brush. After washing, make sure to dry it thoroughly to prevent further rusting. If the rust is severe and affecting the integrity of the sheet pan, it might be time to replace it with a new one to ensure your safety and the quality of your dishes.