... Vaseline as a oxidation preventer with Aluminium connections?
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
Yes, never let PSU currents run through the chassis. This technique belongs to the 1950s era of valve radios, not modern audio. Never let any currents run through the chassis; the chassis is for mechanical mounting, electrostatic screening and electrical safety.
absolutely, i got wind of this idea from working with atx psu's....
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..
Preventing oxidation on aluminum???? Totally impossible; aluminum always has an oxide layer on the surface.
That is why mercury can eat through aluminum. It removes the oxide layer that forms immediately when aluminum is exposed to air
and allows the oxidation to continue until the aluminum is consumed.
Mercury Eats Aluminum! | Science-Based Life
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.
That is when I found out that they had coated the aluminum chassis and covers with a non conductive coating to meet FAA requirements. The fix was to replace a non-shielded inductor with a shielded one. Strange things happen at 4.3GHZ. Also it worked if you removed the coating from the aluminum.
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.
Any experience using Vaseline as a oxidation preventer with Aluminium connections?
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.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..
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Are you kidding ? Stainless steel is a steel alloy with a lot of Nickel.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 chemist that knows nothing about metallurgy.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.
Here we have confusion with steel hardening.
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
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.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.
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.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.
In fact, "galvanizing" the wrong way
...just to use copper plated ally busses.
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.
I am not aware of Copper plated aluminium. What is it ? How is it made ?
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 iscopper plated aluminum wires are now being common place for cheap consumer goods coming out of China...
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.Didn’t Jeff Rowland do a few copper coated heat sinks on some of his products ?
Regards
David
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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