Removing anodizing

Fat Old Guy

Fat Old Guy

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I mentioned in another thread that I picked up an old Model 38 Airweight. Most of the blue is gone from the frame and I'd like to remove the rest of it and polish the gun, leaving the steel parts blue.

What should I use? Automotive rubbing compound? Jeweler's rouge? 0000 steel wool?
 
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Lye (sodium hydroxide) solution quickly and effectively removes anodizing from aluminum parts.

It is caustic and an etchant, so you have to take appropriant precautions and use protective equipment: eye and face protection, rubber gloves, protective clothing, etc. You also have to watch the action carefully and remove as soon as the anodizing is gone.

Common "Draino" or Red Devil drain cleaner is lye crystals with chips of aluminum in it. Mix in an acid proof container (plastic bucket or stainless cookware) enough solution to completely immerse the object.

Using plastic-coated wire for handles, dip the object into the lye. Watch the bubbles and black anodizing come off. This action will take only a minute or two. Remove from lye when all color and anodizing are gone and rinse off in water. Dispose of lye by pouring down drain or toilet.

You can now hand polish using 400 grit wet-or-dry abrasive or 00 steel wool to polish as you want to get a nice natural aluminum finish.
 
Works very effectively.
Take particular note of John's instructions to watch the process very carefully and remove as soon as the annodize color is gone and rinse.

If you leave the aluminum frame in the lye solution,,the lye will also begin to break down and eat away the frame itself.
Depending on how long it's left in there and how much solution, anything from pitting, to severe cratering and metal loss, to 'gone' can occure.
 
2152hq, thank you for the added cautions.

The anodizing is only a few tenths of thousandths of an inch thick. That's why it is removed in only a minute or so and rinsed to stop the etching action. Done correctly, there is no measurable dimensional changes.
 
Indeed using caustic chemicals is perilous, but the advantages are great.

Yes, you can abrade the anodized finish off, but you will find it extremely tedious and very time consuming. It is also impossible to remove the anodizing from the bottom of rollmarkings and machine tool marks, requiring more abrading. Even when done, you will still have many black marks from anodizing at the bottom of machine cuts and crevices. All of that hand polishing results in significant dimensional changes even when done with care and skill.

I have sucessfully stripped anodizing from Ruger SA revolver grips, S&W M39 frames, .22 rifle and shotgun receivers, and such. After stripping, the part can be left a natural aluminum finish or be coated with sprayed-on baked coating for darker finish and increased durability.
 
Anodizing is a form of electoplating, so various other plated finishes would work. I recall hard chroming a model 39 frame-Armaloy actually-for a customer back when. The Armoloy produces a very hard (70-74 Rc) wear resistant coating less than one thousanth of an inch thick and molecularly bonded to the base metal.
 
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Correct me if I'm wrong. But anodizing is far more than just a simple surface / color treatment. It actually changes the molecular structure of the surface aluminum, increasing hardness and density, as well as protection against oxidation/corrosion.

So, chemically removing the finish would leave the bare aluminum exposed. No?
 
oliveview you are correct. you also can only re-anodize the frame 1 more time before critical dimensions change. the local anodizing company I have used will not do it for me unless I assure them it is only the 2nd time. I beadblast off the factory anodizing and the beads I use get down into all the lettering. You also cannot hard chrome over bare aluminum, they have to use electroless nickle first then chrome it. I did my son's Sig 229 that he carried in the Border Patrol and that is how they did the frame. Still looks good. He's an ICE agent now and they don't allow different looking guns so it is retired.
 
Leaving the blue in the lettering would be fine because I normally color my marks and lettering so that they are visible.

Much to think about.
 
oliveview said:
So, chemically removing the finish would leave the bare aluminum exposed. No?
Click to expand...

Bare aluminum oxidizes very rapidly and the oxidized surface provides a coating that protects the rest of the metal. Think of airplanes.
 
What will the lye do to the steel parts that cannot be easily removed, like the barrel?
 
The lye bath will not etch blued steel parts except degrease it.

In fact, I have left steel coat hangers in bluing solution (saturated lye) for months at a time, and they don't even rust.
 
Anodizing is like case hardening for aluminum. Anodizing (aluminum oxide) approaches the hardness of diamonds and it protects the underlying soft aluminum. The unprotected soft aluminum frame would quickly wear from use. The color on your frame is a dye that has been added to the porous aluminum oxide surface layer. Just because the color is gone does not mean the surface layer has been worn through.

If you are concerned with the appearance of the gun, this would be a good application for one of the bake on paints like Ceracoat. Smith & Wesson paints the new airweights.

Lye is also an effective bluing remover, I use it in the shop to strip bluing from guns.
 
Pat_Jones said:
Anodizing is like case hardening for aluminum. Anodizing (aluminum oxide) approaches the hardness of diamonds and it protects the underlying soft aluminum.
Click to expand...

So, in your opinion, soaking my gun in lye to remove the blue is a BAD thing.

So is there an easy way to remove the blue dye without destroying the gun?

As for new finishes. Looking at Brownells there is Ceracoat, Duracoat, and Guncoat and a teflon/moly finish. All of which seem to be able to be applied with the airbrush that I used to use for modeling. Any thoughts on which one to use and why or better yet, which one not to use and why?

Also would I have to strip the bluing from the steel parts for these spray on finishes?
 
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