Do you mean the feeder bins or the wire that the rats eat through?
Regarding the latter, even the expensive laboratory style cages require the rats to eat through wire so I assume their teeth can take it. Given the heavy scrutiny that science labs are under I assume it's considered fine.
Rats can eat through 1/2" x 1/2" welded wire mesh or hardware cloth. The "hoppers" cannot escape through it whereas hopper mice can.
The only problem with the 1/2" x 1/2" is that the rats don't have to chew on the food very long before it falls through. This creates a situation where much of the food is dirtied.
If the food falling through is a concern then there are better choices, albeit more expensive and difficult to find.
1/3" x 1/3" or 3/8" x 3/8" hardware cloth work for both mice and rats. 1/2" x 1/4" welded wire also works for both.