I have seen evidence of this myself with a WW1 MkIV tank that has sat in a square in my home town since 1919. Recently, the council wanted some conservation work done on it and I was brought in by one of the potential contractors. The steel plates on the side were cracked and pulled out of line by rust that had foced the riveted joints apart. Discussing this with Bovington Tank Museum, it is not unusual. The steel plate used and the hardening procedure was to blame, you have to remember, armour plate was in its infancy at that time, doubtful they were using alloy mixes, more like flame hardened boiler plate, I suspect. Welding the cracks would have made the problem worse, all in all, to restore one of these to usable condition, you would end up reconstructing the hull, then the originality has gone out of the window. Sad as it is, they are best left to rest in peace now as static displays.
And someone else got the conservation job. One interesting I spotted though, when inside it, both of the huge drive chains were in place. From information I had picked up before, one drive chain was removed from all these tanks that were in place all around the country as war memorials, so that they could not be driven and used in any civil uprising.
Richard