Excellent post
@KeroZen!
This is exactly the sort of stuff I've been reading through, I actually read through that willow.co.uk article already a few weeks ago. Interesting stuff!
I've been looking at a lot of examples of how they solves these issues in industry, especially with high current applications. And yes, it does seem like using noble metal coatings is the way to go to avoid oxidation. There are a number of interesting solutions used in relays and large connectors that are pretty neat as well.
I actually sampled a few connectors, all of them gold plated. But non of them felt quite right. I opted for a more simple approach.
Originally, I was going to go for gold plated contact surfaces all around.
But, then I got more into reading about mechanical mods. Here is another related field that has already dealt with all of the exact same problems. When you get into plated vs. non plated contact points, or even solid silver contacts.. the performance differences are pretty much nill'.
Oxidation is not the only barrier to a good electrically conductive contact. Regardless of metal, the contacts need to be kept clean of oil, dirt, dust, etc..
This is why I went with a design that enabled easy disassembly and cleaning of all contact surfaces.
Mechanical mod users seem to clean their contacts quite often, I think it's just a requirement.
And yes, brass definitely does not provide the best corrosion resistance, it's just a good compromise IMO.
That said, the only all brass connection is in the button. I would love to be able to offer gold plated contact points in the button to those who are interested. I looked into it, and proper industrial plating services usually require fairly large minimum orders. Plus, the parts will need to be "masked" off so that only the places I want to get gold plated will get the gold plating.
Alternatively I could get gold plating supplies/tools to do it here in the shop, but that will be a fairly big investment if I want to do it properly....and it needs to be done properly... I've read a lot of reports of the thin Chinese gold plating they put into mech mods wearing off in no time at all.
To mitigate some of the issues with brass corrosion, I am maximizing contact surface area, and also giving the parts a high polish. All of the parts are cut to a very tight tolerance, no slop or play, so when the contact surfaces are touched, the entire surface will make contact because the parts are not skewed or crooked.
The contact between the battery negative and the brass screw is a sliding connection. This sort of connection is used in connector/relay design to "scrape" away corrosion each time the connection is used. Essentially making it self cleaning.
The screw thread quality will also play a big role. The threaded screw is as long as possible in the solid brass button housing. And since the head of the screw is always tightened down firmly, the flat face of the head will make a better connection with the flat face of the button housing. It's not enough to rely on the threads alone, because there is always some play in even the most accurately cut threads.
This screw should only need to be removed for cleaning, so it should see minimal wear. It's also a fairly beefy thread, as beefy as I could fit.
I will be using silver contacts for positive connection between the battery and the heating module.
All of the heater module connections are silver.
Anyhow, If money was no object, I would probably go with selective thick gold plating in the button, silver screw, and silver alloy for all other metals... but for now I am just trying to do the best I can with the resources I have available.
I would be interested to hear more of your thoughts If I missed anything! I love thinking/talking about this stuff!!