Impossible to format corrupted SD card formatted as internal storage
It sounds like the other answer of the FAT being corrupt is likely, I would try "zeroing out" the card...

First, verify the device... it will be something like /dev/sdb or similar, make absolutely sure you know this device is correct. Then, in Linux open terminal and enter the following command:

$ sudo dd if=/dev/zero of=/dev/sdb bs=8192


Substituting the correct device name for /dev/sdb. 

DO NOT interrupt this process or it could possibly brick the SD card.

Once it has completed, eject and remove the card... wait a few seconds then reinsert the card in the card reader. After this, open gparted (or your partition manager of choice) and create a new FAT and partition. In gparted, this is accomplished by selecting Device, then Create Partition Table from the toolbar menu, I would recommend using msdos as the partition type. Then after that process completes, select Partition - New, and change the File System to fat32 (or whatever is appropriate for your card) and click Add. Then Apply (the "return" arrow in the menu bar). 

Once this has been completed, remove the card and reinsert it, it should be readable in Linux, Windows, and most other operating systems.