recommend cheap and corrosion resistant electrical contact material

Apr 17, 2021 Last reply: 5 years ago 13 Replies

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mike daniels 5 years ago

I'm looking for a low cost contact material that can withstand being exposed to unconditioned warehouse conditions for months without the surfaces becoming corroded or oxides.

The shape of these will be similar to D cell batteries with a spring on one side and a flat contact on the other. The device is not a battery but mounts similarly and must work reliable on first install. No jiggling allowed.

The flat contact will mechanically retain a stainless steel spring (304) so this contact metal cannot react with stainless. The spring must be stainless to get the mechanical force we need. No copper or brass here.

My knee jerk reaction is to keep everything the same stainless material. The downside is the battery clip style ones need some bends and shaping that get a little expensive.

The other downside is we the minimum current passing through this contact is 1mA. Not very high to "burn" through oxided layer. We do have 15-30V so that is something but I rather not have to depend on punching through an oxide layer to get contact.

Thoughts are.

1) tinned copper or brass
2) Gold plating "LOL too expensive but maybe not in high enough batch sizes"
3) nickle plated brass, copper, tin?
4) straight tin
5) straight nickle

Any other contact material/plating options stick out as a winner in this application?

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whit3rd 5 years ago

...

Bright nickel plate is good, inexpensive, and... do you really want 304 SS for a spring? Bronze is just as corrosion resistant, and phosphor bronze is a good electric contact material, too. 304 SS can be work hardened, but isn't an optimal spring.

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DecadentLinuxUserNumeroUno 5 years ago

mike daniels snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:

Platinum. Been used for contacts for decades.

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bitrex 5 years ago

If galvanic corrosion with stainless steel is a big concern then brass, tin, and nickel-silver are out I think.

Straight nickel, cupronickel, phosphor bronze, alloy of nickel and chrome would be better choices.

But if it's a low moisture/humidity-controlled environment then galvanic corrosion is not as much of a concern. Stainless steel model train wheels on nickel-silver track has been a go-to for generations of model railroaders...

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bitrex 5 years ago

Sorry, meant to respond to the OP.

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Joe Gwinn 5 years ago

Yes. The standard material for such applications is beryllium copper. It resembles phosphor bronze, but is far stronger.

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Joe Gwinn

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Clive Arthur 5 years ago

Mould some silver conductive epoxy onto your SS spring.

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mike daniels 5 years ago

Its actually 302 stainless not 304. not sure how much of a differnce that makes.

Thanks for the recommendations.

Another constraint I neglected to mention is that the surface should be solderable with typical leadfree (SAC305) type solders and fluxes. No heavy duty fluxes as it could be soldered directly to a PCBA with solder paste.

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Cydrome Leader 5 years ago

spring copper might work. Strong, can be soldered, doesn't corrode too bad, no small batch plating needed, good track record for electrical use etc.

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Jasen Betts 5 years ago

at such low current how about carbon coated contacts?

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