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Topic: Which chemicals corrode gold?  (Read 20388 times)

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Offline carfo

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Which chemicals corrode gold?
« on: April 16, 2011, 11:55:20 AM »
I work for a jewelry store and many times customers will come in with rings that look like they are being eaten away by chemicals. I think this is probably due to chlorine and maybe some other chemicals inside hand sanitizers, since most of those who come in with this problem are either nurses or spend time in chlorinated pools.

I am aware that gold cannot corrode but many rings are not pure gold and are mixed with alloys (14k for instance is 14/24 gold, 10/24 alloys) which I am sure you are aware of. I tried doing some research on this, but didn't find any legitimate answers.

Any good chemists out there know which specific chemicals in hand sanitizers (etc...) would eat away at the metals inside gold jewelry that would cause it to become brittle and crack? I would like to accurately inform the customers of how to prevent this from happening to them. Thanks to any smart chemist who can answer this!

Offline discodermolide

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Re: Which chemicals corrode gold?
« Reply #1 on: April 16, 2011, 12:29:20 PM »
I work for a jewelry store and many times customers will come in with rings that look like they are being eaten away by chemicals. I think this is probably due to chlorine and maybe some other chemicals inside hand sanitizers, since most of those who come in with this problem are either nurses or spend time in chlorinated pools.

I am aware that gold cannot corrode but many rings are not pure gold and are mixed with alloys (14k for instance is 14/24 gold, 10/24 alloys) which I am sure you are aware of. I tried doing some research on this, but didn't find any legitimate answers.

Any good chemists out there know which specific chemicals in hand sanitizers (etc...) would eat away at the metals inside gold jewelry that would cause it to become brittle and crack? I would like to accurately inform the customers of how to prevent this from happening to them. Thanks to any smart chemist who can answer this!

Gold is attacked by conc nitric acid. If your jewelry store has "corroded gold items" I would suggest that the ire's consist of gold plated items where the gold surface has been scratched away and allowed the corrosive chemicals such as bleach (chlorine) to attack the underlying metal
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Offline ResearchGrad

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Re: Which chemicals corrode gold?
« Reply #2 on: April 16, 2011, 05:50:05 PM »
If you tell your customers the real reason why jewelry get cracks, you will start losing business.  The cause could be from ill preparation of the alloy surface prior to gold plating.  Here is an analogy, if you were to paint a house you want to paint a primer before the final paint coating.  Same applies to jewelry.  But the real culprit is the carbon dioxide in the air that is oxidizing the alloy metal.  We know that gold is inert so that won't be a problem, but the unplated crevice after gold plating being exposed.  You would expect discoloration, scratches and even cracks.  Tell your customer stop swimming in public pools!

Offline AndersHoveland

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Re: Which chemicals corrode gold?
« Reply #3 on: April 16, 2011, 06:59:58 PM »
Chlorine water or bromine water is capable of corroding gold, although the reaction is very slow without the addition of concentrated hydrochloric acid.
http://www.francoiscardarelli.ca/PDF_Files/Article_Cardarelli_Gold_Leaching.pdf

It is very likely that pool water slowly corrodes the surface of even 24 carat gold.

The inertness of gold is mainly caused by extremely weak covalent bonds with oxgen, combined with unusually high ionization energies for a metal. Dissolving gold is actually less about chemical inertness and more a matter of solvation of the surface gold compounds which form.

Offline Honclbrif

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Re: Which chemicals corrode gold?
« Reply #4 on: April 17, 2011, 08:38:32 AM »
Whatever is causing the corrosion, it is probably not hand sanitizer. The active stuff in hand sanitizer is usually ethanol, which won't give gold any trouble. Neither should any of the thickeners or preservatives which make up the remainder.
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Offline Embark04

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Re: Which chemicals corrode gold?
« Reply #5 on: April 17, 2011, 02:07:17 PM »
Aqua regia, a 1:3 (%v/v) solution of nitric and hydrochloric acids. Then again, this will strait up dissolve most metals with some exceptions. 

Offline Sepelio

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Re: Which chemicals corrode gold?
« Reply #6 on: May 10, 2011, 12:38:21 PM »
I was going to say Aqua Regia, but I'd guess you could also have it corroded by liquid metals like Mercury or possibly Gallium. Both might well amalgamate with gold causing it to corrode.

Online Borek

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Re: Which chemicals corrode gold?
« Reply #7 on: May 10, 2011, 03:38:01 PM »
I seem to remember iodine baths for etching gold, for sure air oxygen in the cyanides bath does the trick.
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Offline sachinchavan

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Re: Which chemicals corrode gold?
« Reply #8 on: May 11, 2011, 11:39:05 AM »
Aqua regia ,mercury ,nitric acid,

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