The Burning Question; How much platinum in a hard drive platter?

If you have ever wondered what kind of value is in the Hard Drive Platters then I have found the answer, finally.
I think this is based on '08 prices;

It's taken me just about forever, but I've finally found some way to answer the simple question "How much platinum is in these hard drive platters showing up on Ebay for salvage?" "The Chemistry of Computing" over at extremetech.com (article2/0,2845,1946290,00.asp) has all the facts: surface layer of Co-Cr-Pt alloy is 40-50% platinum, and the layer is ~30 nm thick. I don't have a hard drive platter in front of me, so let's just forget about the hole in the middle for a moment, so one platter from a 3.5" disk is 3.14*(3.5/2)^2=10.4 sq inches or 67.2 cm^2 ... times the 30 nm thickness (3x10^-6 cm) is 2.0x10-4 cm^3, times the (optimistic) 50% Pd, times the density of Pt (21.45 g/cm^3) and I estimate one platter has at most 2.2 mg Pt. As of 08/29/2008, the platinum spot price was 1470.00 USD per troy ounce, or more usefully, 4.73 cents per miligram. So, congratulations, you've just spent an hour of time and three cents of chemicals (just a guess, probably high) to reclaim 10 cents of platinum, probably still contaminated with cobalt and chromium depending on your recovery method. I hope you bought a whole bunch of platters cheap and rode a bike to pick them up because I doubt you'll be paying for gas let alone the shipping with the platinum. Or hope those early hard drives used a much thicker layer....

I have argued and argued with people about the platinum content in hard drive platters for a long time now. I'm glad you found this on your own, and posted it yourself.

You see hard drive platters sell on ebay all the time, people are getting burned left and right. They are really only worth their aluminum content, the Pt is negligible. Not only that but it's only be fairly recently that platinum has been used as as a percentage of the plating on hard drive platters. So all the old hard drive platters don't even have platinum in the plating.

Scott

Originally Posted by CTscrapman

Nice research Mech, so from what i gather people really are buying these platters for art projects and wind chimes . Also FYI not all platters have an aluminum base.

Yep, I found out firsthand that some of them are plated glass. I had one gentleman contact me as he wanted a large quantity of them for putting on the ceiling (hanging by fishing line) in a Disco house. Can you imagine the disco lights hitting a few hundred spinning HD platters.

Originally Posted by NewbyScrapper

They also make great bird scarers. Using them as signalling devices, as long as the sun is shining

Make a energy intensifier, line an old 8 ft. satellite dish with them then aim it towards the sun.
Just need something out front to collect the magnified energy.

Originally Posted by AJR

So along with heat sinks, some floppy casings, and most of the hard drive casings, I could mix the platters in my aluminum scrap bin as well? I pull the boards off the hard drives and sell them separate. I can get about $0.40/lb for the remaining drive. I have about 800 lbs of remaining drives that I wanted to pull apart for the super-duper magnets. I know usually the top cover of the drive is steel, and the rest of the casing is cast aluminum.

Yes, the people I know who scrap hard drives, throw the platters in with their Al...

Scott