Polish Copper and Aluminum - Quick and Easy Mirror Finish

A couple of years ago I made an Instructable showing how I polished a piece of aluminum sheet metal. That method was very time consuming, so I've been looking for an easier method for polishing aluminum. I found a method that works quite well, at least for thick pieces of aluminum. In this Instructable, I'll be showing that method, along with a few different variations that I tried to get the best results. I also tried this same technique on a piece of copper, so I'll also be showing the results for that.

If you would like to see a video version of this Instructable, you can check that out here: https://youtu.be/FiqFERXawz8

If you would like to check out my previous Instructable, you can check that out here: https://www.instructables.com/id/Polish-Aluminum-Sheet-Metal-to-Mirror-Finish

Here is a list of what I used:

Tools

• Scrubbing Pad
• Microfiber Polishing Cloth

Parts

• Aluminum Angle Stock
• Copper Fitting
• Aluminum Sheet Metal

Supplies

• WD40
• Blue Magic Aluminum Polish
• Sandpaper (multi-grits)

I'm starting with a piece of aluminum angle stock. I added a piece of painters tape, just to show the contrast with the original finish when I'm done.

For this first experiment, I'm just using some aluminum polishing paste. With a microfiber cloth, I rub the polishing paste onto the aluminum for about a minute, while applying a bit of pressure. You can see in the final picture here that it gets quite a bit more shiny, but it's not exactly a mirror finish.

For the next experiment, I move to a different side of the aluminum and spray it with some WD40, then I scrub it with a scrubbing pad. Afterwards, I wipe off the WD40 and rub on some polishing paste for about a minute, just like before. This time it gets more shiny than last time. The surface of this piece of aluminum isn't smooth, so the reflection is distorted.

For the final experiment I started by smoothing out the surface. Using 220 grit sandpaper and some WD40, I sanded down the wrinkles. Then I switched to some 400 grit sandpaper and sanded the surface a bit smoother. Next I follow the same process that I did before... I use the scrubbing pad with WD40, then polishing paste for about a minute.

I removed the tape and compare the 3 methods. The first one with just the polishing paste reflects, but it is quite hazy. The second one where I used the scrubbing pad with WD40 before the polishing paste, reflects quite well but the reflection is distorted. The final one that I sanded first has the best results.

Based on the results of these tests, and also the research that I've done, I have found that it's helpful to remove the oxide layer from the surface before you try using the polishing compound. The scrubbing pad works as an abrasive for this, and the WD40 helps with this as well. If the surface isn't already as smooth as you like, sanding the surface helps with that. If you do sand the surface first, that will remove the oxide layer, so the scrubbing pad shouldn't be necessary in this case.

Now let's try this technique on some copper. I used a copper fitting for this. It's already smooth, so I skipped the sanding and started by getting the oxide off of the surface with the scrubbing pad and WD40.

Wiping off the WD40, I rubbed on the same aluminum polishing paste. After about a minute and a half, a portion of the copper is polished. With just a bit more work, I get more of the copper polished. Comparing it with the finish on the aluminum, it's about the same reflective. Since this fitting is curved, the reflective surface of the copper is harder to demonstrate on the camera.

One final experiment that I did was trying this technique on a piece of aluminum sheet metal. Following the same steps, I started by using the scrubbing pad and WD40. Then I used the polishing compound with a microfiber cloth. I found that this does work on the sheet metal, but it does take quite a bit more work than the other pieces of metal that I used for these tests. After using the polishing compound, it also helps to use a clean microfiber cloth to buff the polished area to remove the residue left by the other steps. In the final picture here, you can see that there is a reflection, but it does need more polishing to get it to a good mirror finish. This is enough for a proof of concept though.

If you would like to see a video version of this step, you can check out this video that I made: https://youtu.be/3TYel_-P-9I

Now for a quick summary:

• (optional) Sand the surface smooth with sandpaper, lubricated with WD40.
• Use a scrubbing pad and WD40 to remove the oxide layer.
• After wiping off the WD40, use a microfiber cloth to rub the surface with some aluminum polishing compound. Make sure to apply pressure while rubbing.
• Using a clean microfiber cloth, wipe off the excess residue and buff the surface you just polished.

If you have any tips or suggestions on how I can improve the results, or improve these instructions, please comment to let me know. Thank you for checking out this Instructable!