What are hard drive platters made of?

I took apart a hard drive to start makine AP Digital Light's hard drive clock, but before I cut the slot for the light to come through, I'd like to know what the platters are made of, just in case they have something harmful in them.


blkhawk5 years ago
The platters are made of aluminum and they are coated with a film of magnetic material (I believe that is some type of oxide). It should not be harmful but do take precautions not to aspire any fine dust. Keep us posted about your progress.
TomA53 months ago

from outter-most layer to inner-most layer, the composition of a 3.5" hard drive platter is as follows...5 micron thick layer of cobalt, the magnetic data substrate. 20 micron thick layer of 90% nickel & 10% phosphorus, making the nickel non-magnetic (This layer is present because nickel takes a very high polish and cobalt (the outter-most layer) does not adhere well to the inner-most layer. The inner-most layer is comprised of 96% Aluminum & 4%Magnesium; Aluminum is cheap and lightweight, and magnesium strengthens aluminum.

I happen to work with a Niton X-Ray gun and came across a few hard drive platters at work. So I gunned them :) Heres what I found:

I igrinder the surface to get a more accurate reading, though , despite my best efforts , I may have just ground the nickel deeper into the matetial


But what about the platinum? Shouldn't it be covered with that too?

AndyGadget5 years ago
You're talking about 3.5" drives here, but just a word of warning if anyone's thinking of playing with 2.5" laptop drives. 
I took one of these apart once and bent the platter with my fingers to find what sort of 'metal' it was made of.  It was actually made of metal coated glass and it shattered and showered me with a billion razor-sharp shards.  Apart from a few minor cuts to my fingers I was OK, but I'd have probably lost my sight if I wasn't wearing reading glasses.

mine just shattered. thats why im here.

MichaelM1 ihagy10 months ago

Hahaha! That's why I'm here

qwertyboy (author)  AndyGadget5 years ago
Wow, I had no idea that they were glass. I would have thought they were the same material as a regular hard drive.
I don't know if all the 2.5" ones are glass, but I certainly found out the hard way that the one I was bending was.
boxfreind2 years ago
Also, I am not aware of any toxic materials inside a hard least nothing that would pose any type of health risk. I have taken hundreds of these apart within the last 15 years without any sort of protection and I am just fine.
boxfreind2 years ago
From what I understand, they used to be made of some sort of metal coated with a magnetic layer of nikel. Now days they are made of what is basically a type of glass or ceramic (depends on manufacturer) also coated in Nikel.
Salsands2 years ago
I'll tell you one thing: putting a bare 2.5 hd platter on the surface of an iPad does not make the iPad very happy.
jheinzen3 years ago
The plates themselves are constructed with a combination of metal, glass and ceramics. They are also covered in an extra layer of thin carbon for protection, followed by a layer of magnetic material which is what is manipulated to signify data.
orksecurity5 years ago
GIFY. Typing your question directly into a websearch engine yields Wikipedia's entry as its first hit, which does answer your question.