Gold in Hard drive?

[sgtmajorbuzz]

I have been pulling apart HDDs for scrap for a few months, as I have stacks of them. I have been setting aside the circuit boards and robbing the platters of the small, but very strong, magnets. On the readers, there is normally a copper coil. I noticed that one of the coils from a Western Digital 500 GB was a gold tone, so I pulled it and rubbed it on my stone. It held at 10k, so I tested it with 14k, to which it vanished within a few seconds. So, I rubbed considerably harder, to make sure I got completely through a layer of the very fine wire, and have the same results. I have since looked though, my other HDDs, and they are all copper. The weight, with a little bit of glue in the corners that holds the wire in shape, is .5 grams. Does anybody have any knowledge of solid gold wire being used in laptop HDDs? Or have I come across another alloy that looks like gold, feels like gold, but sure isn't gold? Other than my acid test and magnets, I don't have any other way to verify gold presence.
Thanks for any insight.

(Pics to follow soon)

 

[butcher]

Have you tried a test with stannous chloride?
Have you tired dissolving the wire in nitric acid after inceneration.

Very small gold wire can be used at the reader heads.

It is not likely to be found in the coil of magnet wire, where copper wire makes more sense, although the varnish on the copper wire coil could be a yellow color.

There may also be a slight possibility that they used a gold plated copper wire in the coil with a clear varnish, electricity does like the skin effect of wire.

 

[sgtmajorbuzz]

No, I am fairly new to the gold recovery hobby, so I do not have stannous chloride yet. Here are some Pics. The coil in question is the one on the left. I placed it above the gold button for color comparison.

 

[sgtmajorbuzz]

another pic

 

[sgtmajorbuzz]

I suppose I could melt it and see what happens. That was my first thought, could you even use gold as a coil? It has me perplexed. But I perplex easily

 

[g_axelsson]

Some drives uses aluminum in the voice coil (the wire coil between the magnets). Aluminum stands up to the 10k test acid which is diluted nitric acid. The color comes from the coating on top of the white metal.

To suggest that the voice coil would be made from gold is failing all "reality checks", is it reasonable to use gold here instead of other materials?
- Hard disks is a high volume product, millions of units is made daily (around 600 million units last year), with half a gram coil per disk it would add up to half a ton gold per million units.
- There is no advantage of using gold in a wire instead of copper, gold is a worse conductor than copper.
- There are no problem with contact corrosion since there are no contacts on the voice coil.
- Gold is heavier than other alternatives,that would slow down the movement and the speed of the hard disk. (seek time)
- You should be able to feel the difference in density in your hand.

Test the wire with a drop of hydrochloric acid, it would dissolve the aluminum wire totally.

Göran

 

[Claudie]

I have ran into them before, they do look like Gold but they seemed to light to me. Gold is heavy. I suspected anodized Aluminum. I didn't test any, mostly because I couldn't understand why so much Gold would be used in such a place. :|

 

[g_axelsson]

Not anodized, covered by a thin layer of plastics, usually formvar or some other though plastic.
http://en.wikipedia.org/wiki/Magnet_wire
The coating can have several different colors.

Göran

 

[sgtmajorbuzz]

Thank you all for your answers. I have no illusions that it is gold. Call it OCD, but I cant just finish with "it's not gold", I have to figure out what it is. It took me 3 months to figure out the composition of a ring I found. It tested positive up to 22k gold and Platinum, yet the entire ring only weighed .3 grams. It turned out to be an alloy similar to dental fillings.