[b06dqn]

How long does it take copper to oxidize?

I took apart an old mobile phone and I'm trying to find out what metal is used in the circuit board and the keyboard connectors.
It can be gold or copper for their conductor properties, lack of magnetism and heat distribution.

The metal used on circuit board and the keyboard connectors has a yellow gold shine and it doesn't seem to be attracted to a magnet. Around the face of the phone, surrounding the display on the inside is a metal that is clearly copper (it's a darker orange compared with the metal on the circuit board)
I scratched it a little to clear off any kind of protection. If it's copper it should oxidize, but my question is how long does it take to observe the oxidation (as a color change to green or blue like an old penny).
Burying it in the garden and waiting for 40 years is out of the question, so if you have any other way of telling if it's copper please share 

Could this metal be something else besides gold or copper?


I've attached a few photos.

[Stepan]

On most contacts it would be a copper alloy. On some spots it can be gold plated (a few mg the most= a few cents)

[b06dqn]

I know that gold plating in electronics is around 2-6 microns thick so on a mobile phone the amount is very small.

I'm looking for a simple way to distinguish copper from gold on electronic devices to find a method of recovering these metals.

I'm actually searching for information on recycling old electronics, and how it's done the safe way, what can be recovered and reused, I'm sorry if my question came out of context in any way I'm just trying to ask specific questions to get specific answers.

Of course I've already stumbled upon lots of pages about "aqua regia" method of recovering precious metals but that rises even more questions (like how to safely dispose of the remains) and is not my only goal.
 
I'm sick of seeing piles of old electronics, and in my country electronic recycling is a joke that is more dangerous to the environment that actually dumping it on the side of the road.

So for now I repeat my question: How to distinguish copper from gold?
I've already found a gold tester kits but I think it costs more that I will be able to recover with it.

So i think a copper testing will be more efficient.

Looking forward to any suggestions.

[Stepan]

You question is quite simple. The problem is that the test require use of toxic and potentially dangerous ingredient, and it is not clear if you can have access to chemicals and proper laboratory equipment. 

[yufgyfyu]

Try flame tests.

[fledarmus]

If you dip copper in a salt/vinegar solution and let it air-dry, you should get a rapid verdigris formation that won't happen to gold. This used to be a common elementary school demo - http://chemistry.about.com/cs/demonstrations/a/aa022204a.htm

[Enthalpy]

Contacts in electronic devices are never made of pure copper. I've seen very few made of brass or printed copper, then plated with tin - extremely bad. Abandoned because it oxidizes too quickly. The universal answer is gold, that's why the electronics industry swallows 30% of gold production. Palladium has been tried from time to time. Silver is too bad.

You should be able to tell just by its aspect, shouldn't you?

After you polish copper or brass with sand paper, its surface oxidizes in air at room temperature within a day. Easy to see.

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To etch copper, you can use FeCl₃ as is done usually to pattern printed circuit. When lukewarm, it takes few minutes for 35µm copper. It won't etch gold.

In case someone wants to recycle gold from cell phones:

Gold is few µm (like 5µm) deposited by a catalytic process over the already patterned 35µm copper, so removing the copper beneath and keeping the gold will be difficult. I'd say: once organics are dissolved and banal metals are etched, dissolve the rest separately in aqua regia, accepting that the copper underneath will mix with gold.

I doubt any selective process catches gold and leaves banal metals. Mercury (mind your health and the environment!) extracts gold from ore, but I believe it selects only free metal (=gold) from oxidized metals (earth).

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If one plans to recycle gold from trashed electronic equipment, he should check the amounts. This activity brings some earnings in Bangladesh for instance. To get rich from that in Luxembourg, it should be done on a huge scale, highly automated, after heavy investments on environment protection - hence Bangladesh.