Why is my pendrive corrupt

There are several possible reasons for a flash drive to become corrupt with the primary reasons being age and removal during a write process.

NAND flash, commonly referred to as flash storage, has a limited life span usually listed as Gigabytes/Terabytes written per year. USB flash drives do not usually list this figure, but basically the NAND flash gets worn out and has a higher chance of it having failures which will start being recognized by computers as corruption.

If a flash drive is removed before it is finished writing all the data to the flash storage it can cause data corruption. Basically when you copy something to your flash drive and you get the copy progress bar, even if says 100% complete that does not mean that it is 100% copied onto the flash storage, it ends up sitting in the storage cache. If the flash drive is removed without ejecting it from the operating system anything in the cache will be lost but the flash drive is expecting a file to be there that isn't and so you get notified of a corruption detected. If the flash drive is properly ejected the cache is flushed and committed to the flash storage to make sure everything is there.

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