I think within a month you will be ripping it out and throwing it away...as the bottom will rust (and will be a pain in the butt to clean - everything will get stuck in it).

Those tubs have smooth bottoms so how are the rats chewing through them...might be simpler to fix the way the tubs meet the top of the rack...I assume you have too much of a gap so the rats are able to get their teeth over the edge and start chewing.

Just an idea.