Copper Polishing/Protection
 

I'm building some ducting with copper sheet, and was wondering how to keep it from re-tarnishing. As a test, I sanded some scrap copper sheet with 2000-grit wet-or-dry, and then followed that up with polishing with brasso. It looked real good at that point.

After rubbing the hell out of the sheet (to make sure all the brasso was gone), I tried applying a thin coat of clear gloss lacquer (bought a can of spray paint from Home Depot).

The paint orange-peeled, and it severely dulled the previously mirror-like shine. Did I miss a step somewhere?

I was wondering - if the paint is going to do this every time, is there any other way to prevent the tarnish from re-appearing without dulling the finish? Maybe automotive car wax or something?

I also picked up a can of clear spray, hoping to do the same.

I'm going to take a guess here, so take it for what it's worth: the finish probably didn't leave anything for the clear coat to hold on to.

Also a guess, I'd try sanding with a lower grit (coarser). Even if there are some visible scratches, the clear coat might bring it out in a nice way, but it'd be experimenting.

think u need cellulose laqcuer (re: blade runners finishings), i tried with acrylic only to have it flake off, yet to try cellulose

@BigBen2K

I was considering that, but if I re-sand and shoot it with more paint, I'd be more apt to use an opaque color instead of clear. I want the copper to be the primary source of sheen and reflection, not the paint.

Don't people do that with waterblocks all the time?

Maybe the brasso is leaving a "protective" film on the metal, and I need to wipe the surface down with something like alchohol or acetone or Tarnex before painting it...

Maybe enamel would be better since this is just duct and not a waterblock...

@logosmani

Hmmmm, I don't know what kind of lacquer I bought. With my luck, nobody locally carries it... :)

Yes, brasso does indeed leave a residue. I don't know if removing it would help.

Edit: refrased.

Yes, Brasso leaves a deposit. Acetone should cure it.

clear coats will almost all tint the bare metal to some degree,
they're not 100% clear. they usually have a slight amber or silvery tint. (there are some that are 100%, but I've never seen them in a spay can and most likely need other paint to adhere to.)
It isn't noticible on most stuff as there is a color and/or not near as much shine as bare metal.

Acetone should clean the copper, you should also wash it with soap and water after.
2000grit is too high for the clear coat to stick to bare metal.

Have you thought about just waxing it? if it's not going to be in contact w the cpu and all that?

I used 1/4 in copper pipe for curtain rods. I just buffed the crap out of them (hard to do to round objects) then used carwav on them. It has the added bonus of entertaining me when the cat tries to walk across them.

I would think that the added shining with Brasso would just decrease the ability of the clear lacquer to stick to the metal (even after the metal is washed).

Does the car wax keep the tarnish from returning?

BTW, I'm not worried about the tint so much, as long as it doesn't cloud the surface.

Update:

I found this stuff called "Everbright". It's a self-levelling protective coating for all bare metals. It can be wiped on, sprayed on, or the part being coated can be dipped.

It's pricey ($26 for a 13-oz aerosol can), but it looks like it's suitable for the task at hand.

Here's a link to their website:

http://www.everbrite.net/

I've been looking for that, but could not recall what it was named. Thanks.
the 4oz can is only $10, and is listed as covering 30 - 35sqft.
If this is the stuff I used before (I think it is) it goes on real nice and even with just a brush.

Can it be used on a waterblock?

I wouldn't as it is a coating

I just got off the pjhone with their tech guy, and he said that the stuff is good for up to 600 degrees F.

I would think that as long as you don't get it on the bottom side, you should be fine.