Well for what it's worth there is a TSB on this, but that doesn't mean GM will cover the repair under warranty. Since the TSB is copyrighted I will only post a portion of it here. Do a search and you can find it.
#PI0564B: Wax Coating on Frame Peeling, Metal Shows Corrosion/Rusting - (Jun 29, 2012)
Subject:
Wax Coating on Frame Peeling, Metal Shows Corrosion/Rusting
Models:
2011-2013 Cadillac Escalade, Escalade ESV, Escalade EXT
2011-2013 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2011-2013 GMC Sierra, Yukon, Yukon XL
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This PI is being revised to add models and model years. Please discard PI0564A.
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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern
Some customers may comment that areas of the frame wax coating are peeling off and rust/corrosion is visible on the metal in these areas.
Recommendation/Instructions
A specialized metal coating product, Rust Bullet?, has been found to be the most suitable product to provide corrosion control and protection to address this type of repair. Our recommendation is to use the Rust Bullet? Automotive Formula* and the Rust Bullet BlackShell?* and that they must be applied according to the manufacturer?s procedures.