My Kobalt wrench is rusting is that something covered by warranty?

No, rusting is not covered by warranty. Rusting occurs when the product is not properly cared for. The pipe wrench is made of steel and steel will rust when exposed to water (the surface will oxidize [rust]). After the tool gets wet, if should be dried off and a light oil applied. This will help prevent oxidation. The tool should be stored with a thin layer of oil to help prevent oxidation from humidity too.