So, these are the 3 drives of which I have the most 'stock' :-)
It appears image uploading doesn't work, so these are the links:
https://imgur.com/y0XwOOO
https://imgur.com/v2HwkFA
https://imgur.com/5mGeHSA
In terms of corrosion, as per your request, the pictures below show the 'worst' state...