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What's the best way to remove the black anodized finish from aluminum parts without removing too much metal? I want to polish the grip frame and ejector tod housing on my Ruger Blackhawk, or maybe give them a matte finish.
 

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Nyghtfall said:
What's the best way to remove the black anodized finish from aluminum parts without removing too much metal? I want to polish the grip frame and ejector tod housing on my Ruger Blackhawk, or maybe give them a matte finish.
You could grit-blast the aluminum parts, but................................if you recall, anodizing is a process where the aluminum is oxidized, Al2O3, I believe. This finish is quite hard in comparison to the native aluminum metal and is more resistant to wear. If you want a matte finish, it should be re-anodized by a local plating facility after grit blast.

Jim
 

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Grit blasting will cause you grief. Any small inconsistancies in the thickness of the anodizing (as through any wear)will allow the grit to etch the softer aluminum to a greater degree. The result is a very uneven surface... I would advise very careful hand polishing with synthetic (ceramic would be best) grit papers (wet or dry) used wet. Remember aluminum will begin oxidizing almost immediately and will become a dull gray in color. Anodizing simply speeds up the process and then colors the resulting oxide layer. In effect you are dealing with aluminum oxide, which is commonly used as an abrasive!!! The bare aluminum will have to be protected for it to retain any polish..
 

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removing anodized finish

The quickest and easiest way I've found to remove anodized finishes is to use lye solution. I've used it to remove anodizing from Ruger revolver grip frames and ejector housings down to base metal before final polishing.

Common household lye (sodium hydroxide) in the form of Draino brand drain cleaning product. It's in the form of lye crystals with bits of aluminum chips to make it "bubble" when clearing drains.

You gotta be CAREFUL using this stuff!! Wear eye and face protection (goggles, glasses, face shield), rubber gloves, and protective clothing. Lye will eat skin, organic materials, and can easily blind you. Work near a source or running tap water for quick rinsing and disposal of used lye.

Add lye crystals to a few cups of water in a stainless cooking pan.
Don't use plastics or rubber.... the lye will eat the container!

The solution will get hot as you mix the lye crystals (exothermic).
The concentration is not critcal. Use say, 1/2 can for about a quart of water.

Using wire coat hangers, dangle the part in the solution, and move it around. Be prepared for considerable bubbling and foaming. Depending on the concentration, the temperature, and the amount of anodizing, the lye will eat through to bare metal within a minute or two. Remove the part, rinse off in clean water, and examine. If there are any missed parts, re-immerse briefly.

Dispose of solution just like you would used drain cleaner. You can safely pour it down the drain.

CAUTION: The ly may be harmful for septic tanks (kill the bacteria) and cause drainage problems.
 

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Perhaps I'm wrong but the aluminum chips are destroyed by the lye when water is added. The gas given off is helpful in freeing the clogged drain. Would not the lye also damage the aluminum part as well as remove the anodizing?? Depending on the part in question demensions may be critical.. but then I'm not as chemist.. Still I believe I'll stick to physically removing the anodizing...
 

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gunnut 69,
You are correct about the lye (opposite of acid is a base) attacking the aluminum...even more so than the anodized surfaces. In commercial circles it's called "Chem Milling" and is used to removed material by etching.
 
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