# Can HA be polished?



## Ty_Bower (Oct 8, 2005)

The HA finish on my Arc LSH and its tailpiece don't match. No big surprise there. I'd never expect the HA to match on two difference pieces.

The head is lighter, and the tail is a little darker. No big deal. The part that bugs me is the head piece is smoother and shiny-er too. The tail is duller, and it even feels "flat" to the touch.

Most of the other few hard anodized parts I own have a somewhat light glossy finish to them. I'm not talking the full on gloss finish you would see on a type II anodize, but they still have a little luster. This tail piece is just really dull.

I don't care about the coloration, but I would like it to be a little glossier. Is this possible? Can HA be polished? Would a little wax do any good?

I definately do NOT want to strip the HA finish in any way.


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## gadget_lover (Oct 8, 2005)

There are waxes and there are polishes. My understanding is that a good wax will work fine without rubbing anything off. 

A polish will contain abrasives, or so I've been told.

Daniel


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## pbarrette (Oct 9, 2005)

Hi Ty,

You could try boiling it in distilled water for ~5-10 minutes or so. It's possible that the sealing process wasn't fully completed. Boiling may help close the pores of the HA and brighten up the finish.

Of course, this would only work if the sealing process wasn't complete during the original anodization process. But it can't hurt, so it's worth a shot.

pb


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## AtomSphere (Oct 9, 2005)

pbarrette said:


> Hi Ty,
> 
> You could try boiling it in distilled water for ~5-10 minutes or so. It's possible that the sealing process wasn't fully completed. Boiling may help close the pores of the HA and brighten up the finish.
> 
> ...


 
Think thats kindda bad right? Don't think surefire's aluminums are heat treated as THEY cut out flashlights from blocks of aluminum. Heat + Aluminum = weaker aluminum?:shrug:


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## Iron_Man (Oct 9, 2005)

No, it can not. As ya thought, use a wax or some such.


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## pbarrette (Oct 9, 2005)

Hi AtomSphere,

Heat treating of aluminum is generally done at higher temperatures than the 100-deg-C of boiling water. Even "Precipitation" heat treatment (also called "Artificial Aging") is done in a range of approximately 120-200-deg-C and is generally left at that temperature for 5 or more hours to reach a state where the structure of the metal is affected.

The anodizing process generally consists of 4 steps:
1) Cleaning.
2) Anodizing.
3) Dyeing.
4) Sealing.

Anodization of aluminum is the formation of Aluminum Oxide crystals which are grown into and out of the surface of the aluminum. The crystals have a porous structure which allows them to accept the dye. The dye generally sits in the bottom of the pores as opposed to being chemically bonded to the aluminum or the aluminum-oxide.

To prevent the dye from leaching out, sealing of the pores is necessary. The sealing step is generally done by boiling the part in distilled water for up to 20 minutes. In commercial applications a Nickel Acetate based sealer is usually used at a slightly lower temperature. Sealing the pores of the anodized surface converts some of the surface of the aluminum-oxide into alumina-hydrate which is a more solid, larger, hydrated form of aluminm-oxide. These larger, hydrated molecules block the pores of the anodized surface and trap the dye in the pits.

If the sealing process wasn't run long enough, then it is possible that boiling will help seal the remaining pores in the anodized surface. This would also result in a slightly more shiny surface since the sealed pores would reflect more light than the unsealed pores.

pb

EDIT:

I forgot to add that heat treating of aluminum is usually done to strengthen the aluminum as opposed to making it weaker. Heat treatment of aluminum is also generally done before the part is machined as well. So it's unlikely that Arc (or Surefire, for that matter) would heat treat their parts. Instead, they would likely use pre-treated aluminum stock.

If Arc did use heat treated stock, then the temperature of boiling water would not be high enough to anneal the metal and destroy the strength properties. Also, 6000 and 7000 series aluminum (as generally used in flashlights) will gain strength with age naturally over the course of years. Artificial aging is done to accelerate the process and results in a stronger metal in a shorter period of time. Even so, boiling in water for 10 minutes is extremely unlikely to affect the mechanical properties of the Arc tailcap.

pb


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## tvodrd (Oct 9, 2005)

Recollections from almost 30 years ago (and a materials handbook in front of me  ) indicate that for 6061 Aluminum, heat treatment for max strength requires "solution treatment" at 985degF for a "soak" time sufficient for the Mg, Si, Cr, and Cu alloying constituents to go into "solid solution." The material is then quenched in water to room temp. This results in the "annealed condition or T0 condition." Subsequent to solution treatment, the material is then "artificially-aged" by heating it to 320-350degF. High strength Al alloys suffer a major strength loss at temperatures approaching their aging temperatures, but it is recovered when the part cools. The T6 after the 6061 means solution-treated and artificially-aged. The 2XXX alloys typically "naturally age," and the solution-treated, naturally-aged condition is called T4. 2XXX series rivits used to be available in T0 and were kept refrigerated which greatly slowed the natural aging process. They were set in the T0 condition and developed their full strength after a few days at room temp. 

The above barely scratches the surface of age-hardening, non ferrous metals! I had a semester of metallurgy, another on heat treating, and a couple more on industrial materials and their properties. It was a veery long time ago! :green: (<---- Disclaimer.)

Larry


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## tvodrd (Oct 9, 2005)

Oh, on the subject of "polishing" HA, It can be done. ~18 years ago we made a complicated, gravity feed track for an automated air flow test machine. The HA build tightened the inside dimensions to the point the acrylic parts wouldn't go. It took diamond paste and a lot of elbow grease, but I opened it the .001" or so it needed. The sucker is still running parts today and the HA is still holding up after many millions of abrasive, acrylic parts. 

Larry


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## AtomSphere (Oct 10, 2005)

Oh..... So simple yet so complex....


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