To store an unused aluminum coil and prevent rusting, follow these steps: 1. Clean the coil thoroughly to remove any dirt or moisture. 2. Apply a thin layer of a rust inhibitor or light oil to the surface. 3. Wrap the coil in a protective plastic or wax paper to prevent moisture and air exposure. 4. Store the coil in a cool, dry place away from direct sunlight and humidity. 5. Ensure the storage area is well-ventilated to prevent condensation. 6. Periodically check the coil for any signs of rust and clean if necessary. By following these steps, you can effectively prevent rusting and maintain the quality of the aluminum coil.