Thread: "HOW-TO" Polish Aluminium? PLEASE HELP

Before you go to too much effort I think that you should check with the "powers that be" as to the legalities of towing a big mirror around ?

I imagine that the blinding glare from this on a nice sunny day could be deadly.

sorry to be a kill joy, john

My understanding of Al is that uncoated, it forms a layer of Al Oxide on it's surface, and it is this that gives it its anti corrosive properties, ie: as soon as you polish it to mirror finish, the mirror finish will disappear, unless you clear coat it with something.
Also, what he said.
TM

Beautiful old van well looked after

Hi re-ali glare the last time I checked a few year ago, the only real problem is rear facing reflective its blinding during the day and at night. The sides isn't such a problem. Double check with RTA regulations. This is why you find such as Fuel trucks & Milk trucks these days have advertising emblazened on the rear. Tippers usually are dull.

There are chemical washes to start with instead of sanding. Sanding is removal of material and you are thinning the thickness each time you sand. Living where you are is corrosive to aircraft type ali of that age and its thin.

The black is normal if you rub your hand on ali enough you'll have the same thing happen.

What polish are you using??

Are you using a Lambs wool buff? These can be washed and reused!

The ali would require sealing again the polish would not be enough.

Aluminium is normally polished with a series of mops and rouge and when done well it does look nice; but, unfortunately it won't stay that way, pretty well everything leaves marks and unless you polish everytime it gets wet or dirty, particularly if you'r near the coast, the surface will oxidize and start looking pretty awfull. The only way to stop the shine from deteriorating is to anodize (although anodizing itself does remove a lot of the shine) or paint it with clear , but unfortunately paint wont stick too well to such a smooth surface. As an ex English M/C restorer, I can tell you the novelty of a nice shiny machine wears off pretty quick when you find yourself spending all of your time polishing it. And as Shedhappens says, I'd check the legalities first.

From a Tech Brief that I've misplaced (of course), NASA found that India Ink was best for final polishing AL. Probably for the Hubble telescope mirror.

Also, what they said.

Cheers,
Joe

Originally Posted by kuttis

When I polish a panel, alot and I mean ALOT of black stuff comes onto the pad and the pad is wasted. What is this black? How do i get rid of it without going through 20 pads?

It's hard to believe but the black stuff is the aluminium metal you are removing as it goes black when it reacts with the cloth and the air. The more you rub the more metal you are removing so don't think it's something that's coating the metal and you are removing something black.

I agree with the others about polishing it. I've made a few things from ally and used to polish them but the novelty wore off pretty quickly.

The black stuff is aluminium oxide. When you buff, cut or scratch ally it almost immediately oxidises ("rusts") on contact with air. This oxide layer is impervious and therefore seals the ally from further attack from oxygen; ie ally doesn't corrode because it corrodes too fast. Confused yet? Anodising is a sort of electroplating process where the item to be treated is forced to be coated with a thicker than normal layer of oxide. If the workpiece is highly polished to begin with the loss of shine is very minimal, but anodising a whole caravan is probably a bit OTT! Incidentally, "coloured" alluminium is made by anodising components, then immediately soaking them in dye. The oxide layer produced by anodising is initially porous and will soak up the dye. This process is vital to the reproductive cycle of "P" platers who understand that blue aluminium shiny bits will not only triple the power of their vehicles but will also draw sexually responsive females in massive numbers

Many chemicals will of course dissolve this oxide layer although caustic ones seem to be more savage than acidic. Salt is a pain, as any Pom who rides classic motorcycles on British winter roads will testify. Mercury is an odd one, it eats through ally by constantly dissolving the oxide layer but allowing oxygen through to continue the process, in WW2 there was a plan to sabotage Axis warplanes by spraying mercury onto the fuselage and wings which would slowly dissolve them.

Ok, lurching precariously back to the original question; you can buy polishing mops that can be attached to angle grinders or polishers. These are used with polishing compound and are very economical. Final polishing is done by hand with cream or liquid polishes, Solvol Autosol or Belgom Alu are probably the best. I can post a piccy for you if necessary, or if you happen to vist Bundy I can lend you the gear ! Once polished a clear lacquer would definately be needed to protect the finish, else dry storage and polishing every weekend

As for the legality of driving around with a big mirror, I have no idea. I do know that getting a blinding flash of sunlight from reflective chrome or ally from a truck bloody hurts!

Originally Posted by shedhappens

Before you go to too much effort I think that you should check with the "powers that be" as to the legalities of towing a big mirror around ?

I imagine that the blinding glare from this on a nice sunny day could be deadly.

sorry to be a kill joy, john

The shine also is of a concern to the speed and red light cameras, not being able to get a satisfactory picture.

This is a pic of my last English bike (any excuse to drag out the photo album will do), The entire crankcase was polished, along with side covers, carbs, hubs, fork legs and other bits and pieces. It took days to finish and turned into a full time job keeping it that way - a van has a lot more more area than a bike. I also tried all sorts of coatings, but none lasted. Like I say the novelty wears of pretty quick.

Ahhh... a post '73 Bonnie. Can I see the rest?

A couple of thoughts spring to mind, firstly, unless your surface is really flat ie, not rippled, then you may actually find that the polished ally doesn't look as good as you hoped. Secondly, I would be very wary of using a barrel grinder and rouge in case you work the metal and stretch it which may, (probably will), cause drumming which will lead to cracking of the sheeting in time.
If you have your heart set on a polished finish, I would first sand very carefully any deep scratches with a sander polisher using 150mm velcro sandpaper of 180 grit, then use 400 grit to smooth the area, finally finishing with perhaps 600 or 800 grit over the whole surface. With all grits lubricate the pad with velvet soap and be aware that the finer you go, the more pads you will use, they must be changed when they smear the ally rather than cutting cleanly. Oh, and keep the pad flat or you will dig holes. Done properly, you will by now have a semi polish on your ally. Next step is to use a 200mm lambswool mop, (I prefer the double sided ones), with 3M cutting compound on your polisher at a slowish speed - too fast dries the compound and throws it all around and polish the sheeting. Finally, finish off with a new lambswool mop and a polish called "purple".
I will warn you that large flat surfaces are the hardest to get an even polish on.
All the different grades of ally polish slightly diffently so what works really well on one, may not be the best process on another.
If it were me I wouldn't go the polished route.

Some aircraft aluminium is "Alclad" - surfaced with a thin layer of pure aluminum which will not corrode. Don't go to heavy with abrasives in case you cut through to the alloy underneath. A Google image search for "polished p51" shows lots of shiny restored Mustangs so it looks doable.
Will look great when you finish!

I have a simillar problem but mine's on checkerplate.

I would like a polished finish and I've done a small test area and it's hard work and doesn't last.

Here's the area I need to polish. In the photo it looks OK but that photo is 6 months old and it's been in a panel shop for 2 months being painted to the aluminium is pretty dead and lifeless now.



I'm looking into POR15 paints to see if I can get an acceptable colour with an acceptable shine that will stick to aluminium and stay attached.

Google "polished aluminium audi" (or similar).
You might need an oil-well or two to pay for the treatment.