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Material selection for exposed contact terminal

harshitr2

Plastic
Joined
Nov 14, 2016
Hello guys, I'm fabricating a simple dock charger for a robot. The robot has two cylindrical copper terminals which gets aligned to a spring loaded copper latch on the dock. A current of around 10 Amps flows through the contact (no arcing, since power is switched on after they are in contact). My vendor gave me an 'Electrical grade' copper tubing and a sheet, but they have turned blackish/dull in few weeks. I haven't tested the difference in conductivity, but I wanted something that would not corrode in open environment (rain, sun, dust and 50 degree ambient temperature). Since this is going to be in production, I would like a material to be easily available. Any other materials you guys suggest? Any special grade of copper? Thanks in advance :)
 
Can you silver plate the copper? Silver will oxidize, but the oxide is still conductive. If the design can provide for some “wipe” ( where the movable and fixed contacts slide across each other) is even better


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Can you silver plate the copper? Silver will oxidize, but the oxide is still conductive. If the design can provide for some “wipe” ( where the movable and fixed contacts slide across each other) is even better


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Can you silver plate the copper? Silver will oxidize, but the oxide is still conductive. If the design can provide for some “wipe” ( where the movable and fixed contacts slide across each other) is even better

Yes, I guess silver plating can be done. I'll just have to check with the vendor. Regarding wipe, each insertion and removal action will result in some 'wipe', so I guess that will be there naturally. Thanks! Don't know about the costing though, as we are playing with silver here.

What voltage?

It's 24V DC.
 
Rhodium plating over silver will be hard to beat: Rockwell A 35 hardness, melts at 1964 deg C and can't be oxidised except in special circumstances. Rhodium plating is used for high reliability switchgear.
 
Nickel plated, tin plated and silver plated copper are all fairly common electrical material. Silver produces nasty whiskers in a chloride/sulfide environment - non-issue if not in that environment. For copper lugs, they are usually nickel plated.

Most likely you can leave bare copper if you coat it with this stuff (Super Corr-A). This stuff is outstanding but expensive. Up to $100 a can. Super Corr-S is very similar but has Teflon in it.

Corrosion Protection| SuperCORR A
 
Tin plating is pretty resistant to many corrosive conditions also, but outdoors is tougher.
 
Nickel plated, tin plated and silver plated copper are all fairly common electrical material. Silver produces nasty whiskers in a chloride/sulfide environment - non-issue if not in that environment. For copper lugs, they are usually nickel plated.

Most likely you can leave bare copper if you coat it with this stuff (Super Corr-A). This stuff is outstanding but expensive. Up to $100 a can. Super Corr-S is very similar but has Teflon in it.

Corrosion Protection| SuperCORR A

Thanks man, nickel and tin look like better alternatives to silver looking at the cost. Lemme do a bit of more research on these! Also, super corr seems quite expensive from a product point of view, and that too has to be imported!

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Thanks man, nickel and tin look like better alternatives to silver looking at the cost. Lemme do a bit of more research on these! Also, super corr seems quite expensive from a product point of view, and that too has to be imported!

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Gold plating is for low-current reliability, not good for power.

If this is a one-off project, consider using hard solder - cadmium silver. File a rectangular shallow groove to contact area (1-2mm deep), fill with solder and file smooth.

This should work and leaves a lot material for wearing, when compared to plating.
 
Thanks guys, Nickel/silver plating looks like the way to go considering cost and vendor availability in my region. Test probe pins can't be used because I'm limited by design, the cylinders contact at the curved sides, not at the face.

Also, this is going to be in production, so can't go with manual soldering method suggested. Thanks for your inputs :)

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Nickel-silver we had problems with in terms of sulfur-type corrosion, and that wan an inside application. Outdoors, there are more sulfur compounds available, and corrosion may be worse than we had.

We ended up tin plating the nickel-silver and that worked well for us. Not sure it will work as well for an application where the contact is used a fair bit, but it may. Use a thicker plating if you do that..

But maybe you mean nickel with silver plating?
 
Nickel-silver we had problems with in terms of sulfur-type corrosion, and that wan an inside application. Outdoors, there are more sulfur compounds available, and corrosion may be worse than we had.

We ended up tin plating the nickel-silver and that worked well for us. Not sure it will work as well for an application where the contact is used a fair bit, but it may. Use a thicker plating if you do that..

But maybe you mean nickel with silver plating?
Oh I was talking nickel or silver plating on copper for better conductivity. What did you use as the base metal? Not copper?

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I am not familiar with the marine environment and the materials used there, but why not stainless steel? Would there be a problem between that and the copper?
 








 
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