To prevent rust on aluminum coils when storing them indoors, ensure that the storage area is clean and dry. Keep the coils away from moisture and humidity, as these can cause oxidation. Use protective wrapping or coverings to shield the coils from dust and airborne moisture. Regularly inspect the coils for any signs of condensation or dampness and address these promptly. Maintain proper ventilation in the storage area to reduce humidity levels. Additionally, avoid stacking the coils directly on the ground; use pallets or racks to elevate them, which helps in air circulation and prevents contact with moisture that could be present on the floor.