TDR Project – First Attempt At Aluminium Polishing

I have a number of aluminium parts for this project that I want to polish but I have never actually done any polishing.  Last Sunday I made my first attempt at aluminium polishing on one of my exhaust end cans.  This blog post describes the method and equipment used.

This is how the exhaust can looked before I started the polishing:

Starting Point

I have read quite a few articles on the internet and watched several videos on YouTube about aluminium poilshing so it felt like I had done my homework over the last 2 weeks.

Here’s a list of tools and consumables that I’ve purchased for aluminium polishing:

• Cheap corded drill.
• Mr. Fastner polishing kit.  Link to product at M&P
• A number of aluminium abrasive flap wheels.  Link to product at MSC/JL Industrial Supply
• Latex gloves.
• Dust mask.
• Eye protection.

The end can did not appear to be heavily scratched or pitted so after reading the instructions that came with the polishing kit I decided to try the coarsest (brown) polishing compound with the hardest polishing mop first.

Brown Polishing Compound (Coarsest Grade)

You can see the yellow string in the mop which will give a mild abrasion.

It soon became clear that this was not abrasive enough as it really wasn’t removing the scratches, pits and grainy appearance of the aluminium.

Exhaust After Polishing With Brown Compound

As the shortcut route had not worked I had to bite the bullet and do things the right way.  I have 4 different aluminium flap wheel grades: 40, 120, 240 and 320.  Starting with the lowest number (coarsest) flap wheel, the whole exhaust was sanded.  The 40 grade was used from left to right (horizontally), the 120 grade was used up and down (vertically), the 240 grade was used from left to right and finally the 320 grade was used up and down.  You get the idea?  You should sand in the opposite direction with each different grade.

Abrasive Flap Wheel

The result of the 40 grade sanding can be a little worrying as it removes any shine that the item may of previously had.  Don’t panic though, honestly.  The 40 grade removes any scratches and leaves a satin finish.  You can see this in the photo below: the bottom half has not been sanded and the top half has been sanded.

Small Area After Sanding

Close-up Of The Result Using The 40 Grade Flapwheel

Whole Exhaust Can After Grade 40 Sanding

Comparison Between Original And Sanded Exhaust Cans

As you work through the sanding grades the finish becomes less “scratched” and more polished.  It can be difficult to see where you have sanded with the next grade though so good light is essential when you are doing this.

Result After 320 Grade Sanding

Now it’s time to go back to your polishing mops and compounds.  As the 320 grade had left a fairly smooth finish I did not bother with the brown compound and harder “string” mop.  The first polishing stage used the blue compound and a stitched mop.  The polishing stages are much quicker and satisfying than the sanding stages but it seems that like all jobs preparation is the key.  Without a decent sanding job you will not get the polished finish you want.

Equipment For First Polishing Compound

Results After Blue/White Polishing Compound

The second (and final) polishing stage uses a felt mop and the green compound.  Just a quick note: when you are using the polishing mops and compounds the aluminium will become blackened by the removed aluminium particles mixing with the polishing compound, just keep going and it will disappear. There is also a pot of lime powder (included in the polishing kit) that can be dusted onto the aluminium and rubbed off to remove any grease.

Equipment For Final Polishing Compound

Result After Final Polishing Compound

For a first attempt at aluminium polishing I was very happy with the results but I had made one mistake which only became apparent at the very end.  The aluminium used in the exhaust can has a “grain” which goes from left to right (horizontally).  This grain could still be seen after the final polishing stage (see photo below).  I think this was a result of using the first sanding grade in the same direction as the “grain”.  I’m going to have another go on this exhaust can but will start with the 40 grade in the opposite direction to the “grain”.

Close Up Before And After

One final tip to end this blog post: after sanding with the 40 grade wheel it became difficult to see where I had sanded with the different grades (120, 24 and 320) so next time I will sand the whole piece with 40 grade but then sand and polish one area completely before moving onto the next area.  Hopefully this will mean that I can clearly see where I have sanded and result in a more thorough sanding stage which in turn will result in a more polished finish.

That is all for now, thanks for reading and good luck if you are trying some aluminium polishing.