How long is the warranty against rust on 2013 Jeep Grand-Cherokee?

There's no specific "rust warranty" on a 2013 Jeep Grand Cherokee, or most vehicles for that matter. Jeep's warranty covers defects in materials and workmanship, but rust is usually considered wear and tear, particularly if it's caused by environmental factors (road salt, etc.). The powertrain warranty (engine, transmission, etc.) might have lasted longer, but it wouldn't cover rust.

To understand what might be covered, you need to look at the original limited warranty provided when the vehicle was new. This usually includes a bumper-to-bumper warranty for a limited time (often 3 years/36,000 miles), and a longer powertrain warranty. However, neither is typically designed to cover rust damage.

If you have rust issues, your best bet is to consult the original warranty documents or contact Jeep customer service. They can tell you what, if anything, might be covered under the terms of the original warranty. Keep in mind that any warranty would likely have expired by now, as 2013 models are over 10 years old.