There's no specific "rust warranty" on a 2010 Chevrolet Silverado 1500. Chevrolet's warranties covered defects in materials and workmanship, not general corrosion from environmental exposure. Rust is typically considered normal wear and tear, unless it's a result of a manufacturing defect (like a hole in the frame from the factory).
If you're concerned about rust, you would need to determine if it's due to a manufacturing defect that might be covered under a previous warranty (which likely expired), or if it's simply environmental rust.
