Aluminum Prop Polishing

[thatguyno1]

I have a piece of cast aluminum I'm trying to sand smooth and polish to a chrome-like finish. Problem is one face has a lot of pinhole and pencil lead size pits (bubbles from the casting) too deep to completely sand out. What can be done to fill the pits and still be able to sand it smooth and polish the surface.

Paul ô¿ô

 

[Great_Bizarro]

Check some of the auto parts stores there is a filler that contains aluminum, just don't remember the name of it.

 

[thatguyno1]

Originally posted by Great_Bizarro@Jan 15 2006, 09:29 PM
Check some of the auto parts stores there is a filler that contains aluminum, just don't remember the name of it.

[snapback]1160121[/snapback]​

Is it fine enough to fill small pinholes??? Will check it out. Thanks

Paul ô¿ô

 

[replicaprops]

I figured Id reply since it is the prop you got from me.

Sanding is all thats needed. If you have a hand held melt sander it will go fast, if not, simply lay some 80 grit on a table face up and rub back and fourth until the surface is flat. Then switch to 120 grit. While your on 120 grit save your sanding dust.

Change direction every now and then. Aluminum folds while its being sanded. Think of it like peening a pipe opening so it folds in.
This folding or peening action makes the porosity of the metal close up.

When you are finished with 120 it will be pretty smooth. If there are any pin holes left, you then take your saved alumium powder and mix it with a drop of 2 part epoxy until its a thick mostly metal paste. The trick here is to make sure the pin holes are empty and clean before rubbing in the epoxy metal powder mix. Use acetone or hydrogen peroxide on a cotton swab to clean it.
When you sand down the epoxy after cure it should look pretty uniform.

 

[thatguyno1]

Thanks Robert. Didn't want to mention the prop for fear someone would take it negatively. I really like the Smallville Air "Stone". My shoulder is worn out from sanding this afternoon LOL. Wish I had known about the aluminum dust - I would have saved some... Didn't think about that.. I have worked my way from 100 to 150 to 220 to 400 and finally 600 grit. It is the bottom of the stone that has the pinholes. Since it is the bottom it isn't really that critical but it's the perfectionist in me. Since I didn't save any of the dust - got any other fillers?? I guess I could get enough if I sand the bottom down some more (plus it would get rid of some of the need to fill).

I still have work to do on the top but it is getting close. The bottom is what needs filling.

 

[Darth Lars]

I have also heard about something called "Durafix" which is a type of solder specifically for aluminum. The manufacturer claims that it could be used for filling holes, but I have no experience with it myself so I can not say more.

 

[Trallis]

i hade an aluminum piece that was totally flat and dull colored I think it even had some rust or soemthing, so i sanded it finer and finer until i was using 1000 grit.

after the thousand grit it was extremely smooth.
But then i had to have the shine.

I came across a product called mother's aluminum polish. you can apply it with a terry towel or something and buff it off with a dremel with a buffing wheel. Or you could buff it off with the terry towel if you dont, but the dremel gives the best results.

When i was done it was a perfect mirror finish.

 

[Marrow Sun]

I've polished aluminum frames on sport bikes before and have delt with the same issues just on a larger scale. I never needed to fill any areas, all the cast aluminum I sanded with 80grit to get to the flattened out stage. Work your way to 320 grit sandpaper then wet sand in ONE DIRECTION ONLY if your looking for a mirror finish. You want to keep wetsanding the piece while going up it grit, 600 then 1000. Anything after 1000 grit you will accually start making the aluminum appear "Foggy" for lack of a better word. To finish it all of I too agree that MOTHER'S ALUMINUM POLISH is best. You can accually wetsand with 1000 grit and the polish together. Then wipe it clean and polish it again with a soft cloth and buff (IN 1 direction) to a mirror finish.

 

[Sporak]

I'll just throw this in...I use a nail buffer to polish aluminum, and brass etc...one of those 3 in one buffers...where the last pass is done with the grey rubber...works wonderfully.

 

[thatguyno1]

Thanks for all the great advice guys. I just happened to find some of that Mother's Mag and Aluminum polish today and used it on the top. As you can see I still have a little fine sanding to do but it is looking better. So far I haven't wet sanded anything but I intend to do that up to 600 grit or finer. As far as the bottom - I'm going to go back to the 100 grit and take more off the bottom. That should eliminate a lot of the pits and this time I will save the aluminum dust to mix with epoxy if I need to. I'm still going to look for some of the products you have suggested. Things are hectic at work so I might not have any updates for a while.

Paul ô¿ô

 

[thatguyno1]

OK - I resanded all surfaces - wet sanding starting with 220 then 320 then 400 and finally 600. Before I started with the 220 I returned to the bottom face with all the bubbles using 100 then 160 and I saved the sanded aluminum. Instead of removing some of the bubbles I uncovered more so I quit when I had enough aluminum to mix with the epoxy. I did that and filled in all the holes. After all the sanding to get it smooth again all I accomplished was to make the bottom flat and smooth - the bubbles were now just filled in holes but you could still see them as grey spots on a smooth surface. So I just polished the stone and let it go at that. Here is a picture of the top surface polished and in a red cloth like in the Smallville episode. I'm happy with it. Can aluminum be chrome plated?? Maybe some day I will try that.