I also have a 2003 Chevy Tahoe Z71. The rear bumper has never been hit or damaged. It is rusting from the inside out. When I brought it to the attention of the dealer they looked at it and told me it was surface rust. I could probably put my finger through it now it's so flimsy.

Rusty Z71 Bumpers
 

Most of the Z71 bumpers I have looked at are really rusty! The white ones show quicker than other colors. The paint on mine has never been scratched or damaged. I first noticed rust running down from under the plastic covers onto the bumpers. Now I have large bubbles coming from underneath. This is definitely a defect from Chevrolet. I would like to hear if anyone has had warrenty coverage of parts and/or labor.

I was considering removing the bumpers and repainting myself, but after looking really close, they may be too far gone already, and may end up buying new bumpers. I will post again if I find reasonable cost replacements.

Rusted bumbers 2004 tahoe black z71
 

Chevrolet sucks! It is the only thing rusted mainly around the back license plate light. It is a defect. Front one is starting rust on the edges. Black paint is popping off it first. This Tahoe was always garaged. It is shame! It does not even have 60k. Had the dealership look at around 50k and got the run around. Will i ever buy another Tahoe from them.. Hell no! I first thought they might go ahead and fix it. I think once they figured it was going to cost $600 to them, they changed their mind.
I show my friends the rust and warned to stay away. Chevrolet has always had some sort rust on their trucks. I know because my dad has owned at least 5 of them from the past when they were called blazers. The new ones are all plastic...hmm wonder why.. My dad has went ford now. That is probably going to be my next choice!!!
Until then: I will show everyone my rusted bumpers!

I also have a 2003 tahoe with rusty bumpers! Always been well kept!

My Z71 CHEVY TAHOE HAS THE SAME PROBLEM.... IT IS COMPLETE DUST N HOLES.... LICENSE PLATES LIGHTS ARE DANGLING