Galvanized steel will rust over time ... even from just the urine it is exposed to on a daily basis.
The vinegar did not cause the rust ... not in that short period of time.
It only takes about 1 minute to clean with vinegar, if you clean weekly ... if there is a build up of urine or poop, it needs to be repeated several times and use a stiff brush.
Stainless steel is much more expensive, but well worth the price ... Caution: Never clean stainless steel with bleach or abrasives! It will ruin the finish. It can be easily cleaned with vinegar and water or a steam cleaner.
A hand held steam cleaner is one thing I use constantly. It is worth the time and money because it ends up saving you time and money in the long run. Wash and
dry to prevent smudges.
Do not use chemical cleaners made for stainless steel unless you carefully wash away all chemicals. These chemicals are not chinchilla friendly. At least none that I have seen so far.
Jo Ann