Aluminum chassis question...

[Bob Simpson]

I'm building my first aluminum (anodized ) chassis amp.
The grounds are soldered to ( tinned? ) ring connectors and bolted to sanded areas on the chassis.
Am I going to have to worry about/deal with the aluminum oxidizing and screwing up the grounds?
Kind of like houses with aluminum wiring?

Should I alter the grounding scheme, or apply a compound like OxGard to the chassis & ring connectors?

TIA

Bob Simpson

[FYL]

A properly made tight connection is OK for eons. You may add a very small dab of Ox-Gard or similar conductive compound if you wish.

[iknowjohnny]

Use a strong bolt, maybe a grade 8 or such so that you can tighten the heck out of it w/o breaking it. Tighten it till your arm falls off, then finish it off by putting a second nut on top of the first to lock it. That thing will never loosen and if it ever starts making bad contact to corrosion you won't have to worry....it'll happen to the next owner long after you're dead. But seriously, you could also use some of that grease that is used to keep contacts from corroding if you're extremely anal about it. I just doubt thats necassary I imagine worse case scenario it may become less conductive than optimal after many many years. so you could always loosen it and re-tighten after a decade or 2.

[Structo]

I would use a good star washer between the ring and chassis so that it bites into the metal.
Also a good locking nut like a Keps or Nylok nut should hold it well.

[Rick]

If you're really concerned, use the OxyGuard but wipe it up so it's only a thin protective barrier and not enough to insulate the connection, then use the star washer and a lock nut and finally 2nd nut to lock that. It should last long after we're around to worry about it.

By the way, the most important ground connection is the 3rd prong ground wire on the mains cable to the chassis ground. Without that, you may have an electrocution device as much as an amplifier.

[drz400]

I'm building my first aluminum (anodized ) chassis amp.
The grounds are soldered to ( tinned? ) ring connectors and bolted to sanded areas on the chassis.
Am I going to have to worry about/deal with the aluminum oxidizing and screwing up the grounds?
Kind of like houses with aluminum wiring?

Should I alter the grounding scheme, or apply a compound like OxGard to the chassis & ring connectors?

TIA

Bob Simpson

Best to grind off the anodizing and use one point to ground. Anodizing is an insulator. After that it wont matter if the connection is tight

[tubeswell]

In the original post, Bob said that the anodising was already sanded off where the ground lugs were bolted.

Bob - FWIW even oxidised Aluminium conducts well, so that bit is not really an issue - 2CW

[Structo]

Plus if you use the star washer it is going to bite into the metal and I don't think it would oxidise where the washer is in contact with the metal.

[Ken Moon]

The grounds are soldered to ( tinned? ) ring connectors and bolted to sanded areas on the chassis

Wouldn't it be better to polish aluminum to make a good connection, vs sanding it or otherwise roughing it up?

The rougher it is, the less contact area, since you're creating peaks and valleys in the metal.

If you polish it, the aluminum will be flatter (at a microscopic level), giving a lot more contact area.

To create physical binding in order to avoid loosening by turning, a star washer will do the trick.

A niggly point I guess, but a machinist told me this many years ago and it stuck with me for some reason

[Bob Simpson]

Thanks for the answers, guys...
Sometimes I overthink/second guess myself, and
end up not getting anything accomplished.

I won't worry about this one any longer.

Bob

[Zippy]

The grounds are soldered to ( tinned? ) ring connectors and bolted to sanded areas on the chassis

Wouldn't it be better to polish aluminum to make a good connection, vs sanding it or otherwise roughing it up?

A niggly point I guess, but a machinist told me this many years ago and it stuck with me for some reason

Always go to a machinist for advice about electricity.

No, it doesn't make it better - only shinier. Once you have enough contact to provide a good ground, everything else is just yet another parallel path to ground - nothing gained.

[Ken Moon]

Hi Zippy

I'm sure you're just being a little snarky there - of course I wouldn't go to a machinist for electronics advice!

- but the point is still valid - lots of folks mention roughing up metal, thinking it will give a better electrical contact, when that's not necessarily true, other than maybe it cleans the surface some if it's dirty.

Whether or not it matters is another question.

I agree that in most cases it probably doesn't, but if someone is going to go to the trouble to take an extra step like sanding the chassis to get better contact, I was suggesting they might try polishing it instead.

Cheers

[flood]

polishing seems to be an awful lot of work as opposed to just sanding a certain area.

i like the idea with the star washer the best - i think that would probably do the best job.

another question - material compatibility between aluminum and steel. what are the chances of ionic corrosion?

[ampdork]

This may be of some use.

http://www.eaa1000.av.org/technicl/corr ... lvanic.htm

If this link ever dies just search "galvanic table"