I was installing new speakers and headphones today with very sweaty hands and it got me to thinking about how much salt from the sweat it would take to start corroding the USB ports in my laptop (which I was inserting the sweat-covered USBs into - I should have rinsed my hands or something but it’s too late for that.)
Does all salt inevitably cause some corrosion, no matter how little, or does it take a big wallop of salt to do that to electronics inside a computer USB port?
It depends.
If the connector terminals are plated with gold, then salt/salt water won’t corrode them. If they’re tin-plated… not sure.
If the printed circuit board (PCB) has a conformal coating, then it should be fairly immune to salt water. If it doesn’t have a conformal coating, which is common for consumer electronics, then you have a similar issue as above… lead-free solder (usually SAC) that is primarily tin with a small amount of silver, and tin-plated things. And I’m not sure about their susceptibility to salt water corrosion.
I don’t think sweaty hands would do it, at least not right away, over time you might see some green corrosion. If you’re concerned, get some electronics cleaner (like carb cleaner, but for electrical stuff) and spray everything down.
In theory, you could even rinse it with some RODI (ie filtered) water and let it air dry. But I’d start with some electrical cleaner. Maybe some dielectric grease on the friction fit (ie usb) connections for good measure.
Uh…wouldn’t dielectric grease prevent corrosion but prevent the port from working? Maybe USB’s 5 volts can break down the dielectric, but I’d be surprised—accumulated finger grease is enough to make a USB port flaky, let alone silicone dielectric grease.
On the other hand, maybe I’ve misunderstood your proposal.
Is there some corrosion? Sure. Is it visible to the naked eye? No. If salt & other things from hand contact caused corrosion of any significance, there’d be all sorts of rusted up stuff and hardly anything would work. Take the blades of a standard plug for a wall outlet. No special alloy (ok, some are brass) and you’d really have to abuse one to get it rusty. Or light bulb/CFL/LED bases. Or headphone/audio plugs.
My daughter has CF, which causes, among other things, excessively salty sweat. Her electronics didn’t last long, packing it in after a few months or a year or so of use.
Fortunately new meds now reduce this excessive saltiness and she no longer needs to replace phones or other electronics so often.
I’ve had a USB conector fail from salt being near a marine aquarium; there is a salty mist nearby.
That amount of salinity is much greater than that produced by persperation.
What makes you think you got any sweat onto the connector?
Unless you are sweating like Striker from Airplane, there’s no way for wet fingers to touch the contacts on a USB device - they are recessed, and protected by a metal shell, and you don’t put your fingers anywhere near them when plugging or unplugging the device.
I thought the point of dielectric grease is that metal-metal contact is still made - the grease flows easily enough to be pushed out of the way - but the grease remains as a seal around the connection and keeps other contaminants out.
The point of dielectric grease is that it is non conductive. It’s used to prevent electro-chemical corrosion, and to protect high-voltage parts that might destroy or ignite other greases.
There are also conductive greases (carbon, silver soap, whatever). Conductive greases are still non-conductive, but aren’t dielectric. They are used when voltage build up is a bad thing, and a high-resistance leakage path is desired. Because they allow leakage, they are less effective for preventing electro-chemical corrosion.
Because conductive greases are less effective at preventing corrosion, dielectric greases are used. But it’s a stretch to say that the point of dielectric greases is that they flow out of the way – if you use the wrong one, and it leaks into the wrong electrical contact area, your contacts stop working just a certainly as if you put a piece of paper between them.
The point of most greases, mechanically speaking, is explicitly to prevent metal-to-metal contact. “Film strength” is the term of art. Silicone dielectric grease inhibits metal-to-metal contact just like nearly every other oil/grease on the market.
This is a controversial subject in electrical/electronic circles. Some people claim the grease will get between the contacts and inhibit current. Others say it’s a myth, and that the grease is pushed away when the contacts are mated. See this and this for support of the latter.
So when I put dielectric grease on my headlight connectors and the lights still work, what’s going on? My understanding has always been (as stated above) that the grease will, in fact, prevent the flow of electricity (being dielectric), but it gets pushed out of the way by the connectors so they can still make contact, while inhibiting water intrusion.
I am firmly in the camp that applying dielectric grease directly to a contact will not increase the electrical resistance of the contact. But just make sure it is actually dielectric grease, since other greases may be too viscous. This is a good explanation of it.
The U.S military (especially the Air Force) has been doing it for decades. But instead of grease they call it a “lubricant.” MIL-L-87177 is a polyalphaolefin (PAO)-based lubricant that is sprayed directly on electrical contacts. Here is the technical report on it. The report says it “bulletproofs” connectors against chemical and fretting corrosion.
It depends on the contact, the contact current, the contact voltage, the contact design, the operating environment, and the number of operations.
When you specify a contact, part of the specification may be about how good it is at breaking the contact layer, and how good it is a keeping contact, how much voltage is required to make contact, how much current is required / allowed.
I wouldn’t say that it’s controversial in engineering circles. It’s controversial in electrical/electronic circles because many people learn their electronics/electricity as a trade skill, and know only what they learned.
It’s primarily a function of the wiping action of the contacts. Most contacts will have a sufficient amount of wiping action to remove the grease from the A spots and provide a good, gas-sealed, galvanic connection.
