That's what its designed to do according to Seagatehttp://knowledge.seagate.com/articles/en_US/FAQ/201271en
" Full Erase - Fills the entire drive with zeros. It can be used to recover bad sectors"
Its magnetic media, not necessarily a physical defect. Maybe some reinitialization since its able to set everything to zero it could use a stronger field without worrying about damaging adjacent data. I would still replace it. once a drive stats going it tends to die.