Anodizing at home....

[clm2112]

Well, time to take the plunge into a new skill. I have another lower to etch and put a finish on. Having given the matter a few days thought, I'm going to take a stab at anodizing it myself.

Already have Sulphuric Acid (my employer sells it.) as well as Lye (sodium hydroxide.) A trip to the dollar store yielded a wide-mouth glass jar large enough to accept the lower and a lead anode. The local Jo-Ann fabrics store netted both the dye and the aluminum wire... after the vinyl cutting adventure, the sales staff probably think I'm a terrorist. The grocery store produced a couple gallons of distilled water and a box of baking soda.

Today is the last day of my vacation/deer hunting week. So, I'll will not be doing this for a few days. But, I think I have all the materials in hand to try this out.

 

[Harold]

For an anodizing solution, I use 1 liter of "battery acid" to 2.5 liters of distilled water.

Before I anodize a low receiver I clean it with alconox detergent solution (just soak it for a few minutes); then rinse by dipping it in distilled water (alconox is slightly caustic); bead blast it; soak it again in the the detergent solution; and rinse it again.

After this process I etch it in a 2% lye solution (i.e. about 20 grams of sodium hydroxide dissolved in 1 liter of distilled water). I leave it in the lye solution for about 10 to 15 seconds after I see fine bubbles start to come off the aluminum surface.

Then I soak it in a "desmutting" solution for about 5 minutes. (This apparently removes copper and zinc from the surface). You make this solution using 30 grams/liter of ammonium persulfate, and 50 grams/liter of sodium bisulfate, using distilled water. (This is from U.S. Patent #3373114).

To connect the low receiver to the positive terminal of the power supply, I use a piece of 1/8" aluminum wire. I bend one inch back on itself and squeeze it tight in a vise, and then I twist the doubled-up piece of wire into the threaded hole for the machine screw that holds the pistol grip.

For an anodizing "tank" for low receivers I use a four liter polypropylene kitchen food storage container (I think it's a container generally used for cereals). And I use some 1/8" diameter aluminum wire wound in a spiral of a few turns (roughly hugging the inside diameter of the container), as the cathode.

For an AR-15 low receiver I anodize it for about 90 minutes at a DC current of about 2.7 amps. (I use a DC power supply in a constant current mode). Probably for a "308" low receiver you'd want a higher current, maybe somewhere around 3.5 amps or something like that.

When I remove the part from the anodizing tank, I dip it in distilled water, and then it goes into a crock pot containing a warm dye solution, for about 15 minutes. (I use Caswell black dye and with this process it gives excellent results indistinguishable from a commercial job).

After coming out of the dye solution, I gently shake off any solution and pat it dry with paper towel and then I steam it, i.e., I hold it over a pot of boiling distilled water rotating it gently so the steam hits it on all sides, for about 5 minutes (I use the aluminum wire as a handle). Then I immerse it directly into the boiling distilled water for about 10 more minutes, to finish the process of sealing the pores.

Then I rinse the piece in cold tap water and let it dry. Lastly I rub the receiver down with gun oil. (The dye seems to leave a surface film which the oil rub down seems to remove).

 

[Hvymax]

Next you'll want to try electroplating!!! Even cooler.

 

[clm2112]

Doing prep work. My sacrificial lower has been etched, scotch-brited, and rigged with aluminum wire. Still have to mix up the various bath and get them ready.

I didn't mix any lye, I just looked at the jug of Castrol Super-Clean... which is a solution of sodium hydroxide.

Scrap piece of aluminum is just bubbling away in it.... if this strips the anodizing on this bit and etches it, then it should work as the initial clean and de-grease step of the process.

 

[clm2112]

Pretty damn effective I would say. About a 15 minute bath took off the gold anodizing down to bare aluminum. Need to scrounge around for another glass or plastic container to hold the cleaner and the entire lower.

 

[svt-bansheeman]

Would this work on stainless? Id like to send some 1911 mags to get done.

 

[clm2112]

Ghetto rig in action....

 

[clm2112]

Well, it looked pretty good coming out of the brown dye solution...

But, I think I screwed up and put it into the boiling water to seal it. I probably should have allowed the dye to dry before attempting to seal it. The finished went green and splotchy.

So much for the first try. It's alright, since I planned on painting the lower regardless of how it turned out. The oxide layer is definitely on the metal, and it will not rub off, so it will have the desired corrosion resistant qualities and will not show bright aluminum anyplace the paint wears off.

 

[Hvymax]

Well, it looked pretty good coming out of the brown dye solution...

View attachment 16262

But, I think I screwed up and put it into the boiling water to seal it. I probably should have allowed the dye to dry before attempting to seal it. The finished went green and splotchy.

View attachment 16264

So much for the first try. It's alright, since I planned on painting the lower regardless of how it turned out. The oxide layer is definitely on the metal, and it will not rub off, so it will have the desired corrosion resistant qualities and will not show bright aluminum anyplace the paint wears off.

That's the spirit. Find some old broken gold jewelry and plate it!!!

 

[clm2112]

Yeah, I have another lower that I can try this again on in a few weeks, just to see if I can get a better color to it. For now, I've got to clean up the chemicals and the containers before it starts getting dark.

 

[Harold]

IIRC the first things I anodized were some Ruger MK3 receivers I made from aluminum 6061 pipe. It's been a while since I anodized anything so I don't remember many details but I did have some trouble the first few times I tried to do it. Did you rinse the receiver (e.g. by dipping it in distilled water) before putting it in the dye solution? Also when sealing the pores did you boil it in distilled water or just tap water?

 

[Bobster]

I have much larger 1-1/2" tube pieces anodized. I took a tour of the facility (40' tanks) and I think they rinse after every step. I'll have to dig out my notes and pics...

 

[clm2112]

IIRC the first things I anodized were some Ruger MK3 receivers I made from aluminum 6061 pipe. It's been a while since I anodized anything so I don't remember many details but I did have some trouble the first few times I tried to do it. Did you rinse the receiver (e.g. by dipping it in distilled water) before putting it in the dye solution? Also when sealing the pores did you boil it in distilled water or just tap water?

I dipped in distilled water for the rinse between anodizing and dye to remove the acid. I didn't have enough to distilled water to also boil the part, so I resorted to tap water. Probably need more than the four gallons I bought to do this...most was used up in the mixing of the sodium hydroxide, sulfuric acid, and dye baths. That only left a gallon and a half for rinse bath and nothing for the boil.

The distilled used in the rinse bath was the only thing that went down the drain on this run, so it will be the only thing I'll need to purchase for the next attempt.