Restoring underbody protection on a car!

Hello people! I noticed at my vehicle (at the front where you put the jack) on the underbody that the underbody protection is loosening. It peels off on both sides on a 5cm2 surface and it rusts a little. Would like to remove and renew the underbody protection at the place with a drill and a round wire brush. How should I treat the rusty places? I personally would have made the place half-blank, then painted with rust converter, then rusted What is the original underbody protection of cars? These are so hard and resistant – is there something to buy? Know underbody protection on rubber and bitumen basis – but these are not as solid as the stuff that is applied in the factory. My questions to you would be: How exactly do I proceed to treat the said places on the underbody? Which underbody protection should I use? h use? Please ask for your comments!