Electroplating of platinum/palladium etc on copper, brass question

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I am not sure where to put this but anyways, maybe someone here has had the experience and can tell me more about what important things would be necessary to do this. I am looking forward to making some electrical contacts that will have to survive a mercury environment in a sealed inert atmosphere container. My main conducting metal is copper but the part that will touch mercury will create an amalgam so I need to use a coating that is compatible with mercury so probably palladium or platinum for good contact resistance.
In general I am informed about the main steps of electroplating and also have some of the tools necessary.

I guess the main question is how do I get the necessary solution into which the target metal is dispersed and where I can then insert my copper parts and using low voltage DC create the electroplating itself.
I have seen people on youtube take and old harddrive disc dilute off the platinum coating from the disc and then put their parts inside the solution and electroplate them, maybe there is a trusted place where I can simply buy small quantities of forementioned metals?

videos like these make it seem easy but they don't explain the chemicals used in each step and their solution



thanks.
 
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anorlunda

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What metal do they use in the common mercury switches used in thermostats?
 
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I have no idea and googling did not help much either (I did a quick one) but in other switches like tilt switches where a drop of mercury is used they use tungsten or some sort of ferrous metal which doesn't react with mercury.
as for me I need the lowest possible contact resistance, my main wires are copper so I thought I slight layer of platinum or palladium might be great. the amount that I would need probably wouldn't cost a fortune as I'm sure a bunch of catalytic converters contain more of the stuff. I have to still look around maybe there is someone around my place that does this professionally but if not I will have to do it myself, i'm just not that experienced with chemistry so I don't know the acids etc that I would need for this job.
 

anorlunda

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Contact resistance depends on materials, yes. But also contact area. Can you meet your needs with larger contact area?
 
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I think yes , my contact area is already rather big, we are talking about something like 1cm2 or more so in theory I could sacrifice a few miliohms for something easier and cheaper for test purposes just to see whether it works. Well the main task still stands, I have a copper conductor or a brass one and I need to coat its surface (the part that goes into my liquid metal switch) so that it can whitstand mercury.
 

anorlunda

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Then why not just use tungsten as you said? There is no practical difference between contact resistance and resistance of the wires to the device. I don't understand why you are so focused on contact resistance.
 
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well i'm not that focused on contact resistance other than i'm operating with very low voltages , but for the most part I need the easiest durable result that I can get for the sake of a test.
I checked ebay just for fun and found palladium etc solutions are for sale, i don't know whether tungsten can be plated just as easily will have to check that out, basically the cheapest solution will probably win as long as it doesn't react with mercury.
 

Tom.G

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Perhaps look in to cannibalizing a relay or switch with Mercury wetted contacts... or asking a manufacturer of same what materials are in use. They are available for small-signal/audio switching up thru hundreds of amps.

Cheers,
Tom
 
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taking apart old switches won't do me any good, because my contact area is very custom and I need it the exact way it is so I cannot replace it with anything else except ofcourse plate the area itself with mercury resistant finish.
 
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You said 'very low voltages.' Depending on how 'very low,' you need to be aware of thermocouple effects for dissimilar metals.
 

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