is it such a thing as my gas tank corroding

theres no way thats the truth. I have never heard of a tank corroding, especially on a newer car like that. the only possibility is that your lines, if rubber, might have worn out, but again, your car is so new that it couldnt have happened.

I ran over a cinderblock in my E320 4Matic wagon back in like 2004 and dented the gas tank so when it read a quarter it was empty. Thats when you need a new gas tank. You sir, do not need a new gas tank.

I've heard of tanks rusting in vehicles that are pre 1971! But an '02 MB ML500?! Impossible... Though one possibility could be the fuel filler neck. Unlike tanks (that are lined with a neoprene bladder), the filler neck is not. I'm curious to know if MB told you this or a local mechanic. More specifics like fuel odor or leakage in the driveway etc...

Its can happen its also that the tank straps were a little lose a stone or something got between the strap n tank it wore a hole in the tank.

I rusted out the top of a tank in six years. It has thousands of rust craters that would seek gas when I filled over a half tank. Yes gas tanks can rust out. Replacing gas tanks is big business in western New York. They bring used tanks up from the south.

are you sure about the fuel quality, sometimes it depends on! and make sure you close the fuel tank well after filling it in the gas station!