I replaced rear pads/rotors recently and found a lot of rust inside rear caliper piston. A lot I mean HUGE layers of interior piston surface were just peeling away, more on the bottom, than on the inside walls. Bottom seemed to bulge a bit.
There're no leaks, but I wonder, if rust can weaken piston to such extent that fluid pressure will punch a hole in it? I have only 60K miles on it, anyone with high mileage G run into failed rear calipers?

Thank you!