The 2014 Chevrolet Silverado 1500 doesn't have a specific, standalone warranty against rust. Chevrolet's warranties generally cover defects in materials and workmanship, but not rust itself unless it's a direct result of a manufacturing defect. Any rust issues would likely need to be evaluated on a case-by-case basis by a Chevrolet dealer to determine if it's covered under the original bumper-to-bumper warranty (which has likely expired) or any remaining corrosion perforation warranty. The powertrain warranty would also be long expired by now.
In short, you're unlikely to have any remaining warranty coverage for rust on a 2014 vehicle.
