For serious (100+ Ampere) screw compression connections involving Aluminum, the standard in the US is *scratch-brushing* immediately followed by NoAlOx or a competing brand (GB Ox-Gard, Burndy Penetrox A-13).
Noalox
As mentioned above, aluminum quickly gets its own oxide protective layer.
BUT at a chassis grounding point you have different metals in contact: aluminum/iron/solder/copper , so yes, it´s good to add a dab of thick vaseline to insulate the whole battery from air oxygen and dampness.
The telephone guys always cover their outside exposed contacts with thick vaseline, I guess they know something
i can confirm this, having worked in oil and gas refineries plant construction projects before in the 90's and early 2000's, we did use petroleum greases, on bolted connections after those were properly torqued tight..
Oxidation of the surface can be prevented by treating the aluminium first with Alumiprep 33 (a phosphoric acid based cleaner and corrosion remover) and then applying a chrome conversion coating such as Alodine 1201.
Phosphoric acid and chromic acid might be hard to get hold of outside of industrial supply though and for any coating like this is prone to mechanical damage which renders it useless.
There are versions of this coating that are fully conductive - we use it where antennae are bonded to the airframe but still need a decent grounding. Not sure if it would affect the propagation performance of SHF though - I'd be interested to know.
I've successfully used vaseline on car battery terminals for years, but they are lead / brass / steel rather than aluminium so not sure how well it would work.
Stainless steel is basically just steel with oil added while it is molten. The molecules naturally rise to the surface and form a permanent coating, hence, why is does not rust. A famous chemist told me that in person. Actualy he was talking to one of the best knifemakers in the world and I overheard it, and asked him more about it. A professor he was, working at the world chemistry institute in research triangle.
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Are you kidding ? Stainless steel is a steel alloy with a lot of Nickel.
A chemist that knows nothing about metallurgy.
Here we have confusion with steel hardening.
Yeah I use something similar for high current busbar connectors to stop oxidisation/chemical corrosion, of the interfacing surfaces when joining copper and aluminium busbars.
I couldn't tell you the brand name.
However another clever workaround (cost, reliability) is just to use copper plated ally busses.
That´s exactly how I process my aluminum front and back panels before final painting and silkscreening.
With locally available brands of course, such as Sherwin Williams and Wanda.
Used their classic 2 component wash primer and have already bought a can of the new "single component" one but haven´t tried it yet.
I don´t use it for corrosion protection, that´s a bonus, but to strongly stick paint to aluminum surface and keep it there under abuse (guitar amps, you know
)It should, the main problem we fight here is that different metals make perfect batteries in salty or acid environment, creating highly enhanced corrosion.
In fact, "galvanizing" the wrong way
Yes, except the usual need is a half-inch on the end of a 500 foot cable. I am sure they make copper-plated Al wire but the ordinary stuff is just Aluminum. I assume a decent copper-plate would be more expensive than using Al-rated connectors and trained electricians doing a little more work at each end.
By electrolytic processes, but the big problemis that it´s a corrosion accident waitig to happen: copper+aluminum is a nice self-destructive combination under the right circunstances.
The Italians produce *lots* of excellent aluminum so in the 30´s or 40´s they gradually tried to replace expensive copper with cheaper copper clad aluminum in power transmission lines ... it was a disaster, while pure aluminum is fine.
The combination held if unscratched, as in a Lab but when in real world use it was nicked, scratched, crushed inside terminals, it corroded in no time.
Only modern use I know is in speaker voice coils, and there it´s covered in epoxy enamel.
Well, reasonable choice if the device is
a) disposable
b) designed for indoors use
while countrywide power lines are expected to live a long life, minimum 30 years and hoping for 100 if at all possible, and by definition are "exposed to the elements" and then some, from scorching Sun (plus self heating) to snow and ice.
Copper plated Aluminium.
Thanks JMF, "the big problem, it´s a corrosion accident waiting to happen: copper+aluminum is a nice self-destructive combination under the right circunstances." This is exactly the first thougt, I had discovering copper plated aluminim.
I don't know about copper plated aluminium heat sinks.
However, I do know a small slab of copper between transistor case and heatsink can be a worthwhile thermal resistance improvement.
Thanks JMF, "the big problem, it´s a corrosion accident waiting to happen: copper+aluminum is a nice self-destructive combination under the right circunstances." This is exactly the first thougt, I had discovering copper plated aluminim.
I don't know about copper plated aluminium heat sinks.
However, I do know a small slab of copper between transistor case and heatsink can be a worthwhile thermal resistance improvement.
I did not find the information on their site.
How thick is the copper coat ?
In case it is thin, it is about useless as far as cooling is concerned. May be some use under transistor cases, but useless around and the other side.
A trick that makes sense is using a copper slab between the case of the transistor and the aluminium heat sink. That is because heat flows easier in Cu than Al.
Copper conductivity is 390
Aluminium is 237
Brass 69
With true copper ( red ), not brass ( yellow ) an alloy that some confuse with copper. Brass is no good for good heat transfer.
So, a slab of copper, quite thick ( 3mm ) extending around the transistor about 2 cm, would improve cooling, at a small extra cost, far less than using a solid copper heat sink.
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