I've been reading alot on how one can "anodize" a lower, or any aluminum, at home.  This post records my results when I tried this process today.  I had a spare "freebie" 80% blem lower that I drill press milled last year.  I've rattle-canned it, then stripped it.    I've done Alumahyde on it, then stripped it.  You can pretty much say this is my test lower.  The lower functions perfect on all the uppers I have, but it's a spare and cosmetically challenged.  It's pretty beat up and there are alot of scratches/gouges in it.  Before starting anything, I cleaned the piss out of the lower with soap/water, then hit it with brake cleaner, then used the compressor to blow out, then rinsed again with distilled water.  Water did not bead from what I could see so I assumed it was clean.  Was wearing gloves all the time.

First off, here is the plastic tub I used.  Filled with 2qt battery acid (from automotive store) / 2qt distilled water.  Question is, is that the right ratio?  Anode ( - side) is a piece of 1/4" aluminum rod I got at Menards along with a piece of flat aluminum bent several times.  Drilled a hole thru the flat and pushed the rod thru it.  The cathode (+ side) is a piece of bent 1/4" aluminum rod that I cut 1/4-28 threads on and thread into the lower grip screw hole.  Not sure what grade the aluminum is.  If anyone can provide a good source to match the aluminum the lowers are made with, I'd appreciate it.


Here's the power source.  At 2 amps or 10, there would be a lot of "fizzing" going on.  Additionally, I couldn't keep the temp below 103 F.  Left lower in the solution for approx. 1-1/2 hrs.  Was pretty shiny when I removed it, but didn't have the yellow tinge to it as I've seen in other posts.  Any suggestions on controlling temp and how long lower should be in the solution with current on it?



After the 1-1/2hr in the acid solution, I thoroughly rinsed and hit it with a solution of baking soda/distilled water just to make sure the acid was neutralized.  Then into the Rit dye bath for about 2 hrs.  One package of dye in about 1-1/2 gallons of water.  Temp of water was 125-145 deg (electric stove)


Once dyed, I moved it to another pot as shown and let hit hover above the boiling water and let the steam "seal" it for about 30 minutes.  I read in another post that if it was immersed, it would remove some of the dye.


Here are pics of the finshed product.  The scratches/blems are pretty noticeable depending on how the light hits it.  Not sure why some areas did not fill in with color totally either.  Overall, the color depth is good IMHO, but there are a few splotches and the overall lower is "shiny" vs. the anodizing you see from manufacturers.  All in all, for a beat-up lower, I'm somewhat satisfied for a first attempt,  but would like to make it better on the next one.  Those of you that have done this alot, please provide suggestions on what improvements or tips/tricks I could make to make the finished product smoother and more uniform. Sand/buff in advance, etc.?   Thanks in advance.  

Not bad for your first attempt especially considering the equipment you're using.

Do you have any recommendations?  

It looks like you did a pretty good job! I'm on my phone, but it looks to be one of the better home anodizing I've seen. I need to set some time a side to try it myself.

Please don't compare your anodizing to a factory lower's anodizing. Factory is type III and what you did was type II. In general, type II is glossy compared to type III. Maybe try etching the aluminum next time before anodizing.

Scott

It looks pretty good to me as well. I've never used a dye...I just GK after anodizing.

Not sure of your anodizing process, but if you have a buffed/smooth surface your finish will be glossy. If you blast w/Al2O3 or etch in NaOH longer you should have more of a matted finish.

Can you explain how to etch, with what, and what it does?  Thanks.

Al2O3 is aluminum oxide. It's sandblasting material available at Harbor Freight or wherever under "aluminum oxide."

NaOH is lye.

Probably roughs up the surface so it's not so smooth thus making it not look glossy.

Nope.
Glossy/not glossy is a function of the blast media used during prep. You cannot distinguish proper type II form type III without lab equipment. In fact there are lots of AR parts out there that were marketed as "mil spec" which are actually type II and you'd never know it.

OP, your results will improve dramatically with an adjustable current-regulating power supply and etching and desmuting before anodize. Forged lowers have a lot of copper in them which must be etched away from the surface before the anodize. Areas that didn't take dye could be from copper, unclean surface, burning from too much current, or thin anodize layer which can be caused by a number of things (wrong current, wrong temp, wrong acid ratio...) go hit up the Caswell Plating forums for some good info.

Ps- if you blast with 70 grit aluminum oxide before anodize and use commercial anodizing dye you'll get a very nice match to mil spec uppers.

Well, you have tried everything else, you ought to try Parkerizing. You can do it in a solution at about 165 degrees on a Coleman stove. You can apply it to polished or sand blasted surfaces as well. Brownell's has the necessary stuff for it. It is a VERY easy way to put a nice finish on metal. Doesn't work on aluminum though.

Yeah, he should definitely try to parkerize his aluminum lower.

Yea...parkerizing will look great on aluminium!

OP, I'm impressed.

But I do have a question....how did you dispose of the tub of battery acid when you were done?

[Deleted]
 

Please no name calling-aimless

If the surface is shiny before you anodize, it will anodize shiny. Here's the process I use to prep and anodize. Add the steps to dye and seal. Step 3 Etching, removes impurities in the Al and mats the surface. I've also Al2O3 blasted with 120gr after step 2 to mat the surface more and then soaked in acetone again for 15 minutes before going to step 3. Don't use a compressor to blow the part dry because oil vapor from the compressor can contaminate it. I use an inline moisture trap when blasting to minimize contamination.

Hardest chemical to find was the nitric acid. I used pH down by Techniflora which I found at a hydroponics store. It's about 10% strait from the bottle and I bought a quart for about $10.  

Procedure
1.One day prior to anodizing - Add 1 part battery acid (H2SO4) to 3 parts DI H2O. Slowly add acid to H2O. 2 qts battery acid, 1 ½ gal DI water. The solution needs to cool down before anodizing.
2.Degrease – materials: dish soap, Purple Power or Greased Lightening, acetone
Wash with Purple Power, rinse tap water, wash with dish soap, rinse tap water then DI H2O rinse, air dry, soak in acetone 10 minutes. Air dry or DI H2O rinse
3.Etch – Red Devil Lye 2 tablespoons per gallon DI H2O. 120g/L
-Attach AL rod to lower to use as a handle. I use a 1/4" Al rod bought from Ace and threaded 1/4-28 to screw into the pistol grip screw hole.
-NaOH bath 2-5 minutes, agitate every so often until a greyed/blk color forms. It does remove Al so don't let it go too long.  
- Spray DI H2O to rinse off over NaOH bath.
- DI water bath covering lower, agitate, pour off and change water let soak for a few minutes.
4. Desmut – 10% Nitric Acid bath (Techniflora pH down)
-3-5 minute turns white. Agitate in bath.
- Spray bottle with DI water
- DI water bath covering lower, agitate
5.Anodize
-H2SO4 should be at 69° - 72°F, use glass aquarium thermometer.
- Use air stone with aquarium pump to circulate the bath.
-Replace short AL rod on lower with longer rod for anodizing.
-Battery charger - Negative (cathode) to lead/AL in bath, Positive (anode) to AR lower AL rod.
Start at 6V for 5 minutes (mine held at 2A). Switch to 12V for remainder of time (mine held at 3.5A).
Read amperage and calculate time.
If power supply reads 3.5A:

720/3.5 = 206 amp min  
81 sq in/144 in/ft = .5625 sq ft  (81 sq in is the lower surface area)

206 x 0.5625 = 116 min in tank @ 3.5A

Spray bottle with DI water over tank
Soak in DI water, change water soak several minutes

Add your dye steps and seal in hot water

Hope this helps.

I didn't.   Still in the container in my garage.

Not 100% which is why I said in general. Given the same exact prep, generally type II would have more of a gloss (or satin) look to it than type III due to thickness. The thicknesses of type II and type III can actually overlap, but in general type II is thinner than type III. I never said it was impossible to have a flat type II (or even a "glossy" looking type III), hence the reason I suggested etching before home anodizing. "Proper type II" is far from a real spec and probably not something any beginner is going to be able to achieve in their garage with a diy method.

Won't it eat through the plastic?

I made a similar set up at home several years ago using a 5 gallon bucket. The acid is still in it with no problems. It comes in plastic bottles to start with so it is probably good to go for a long time.

The acid solution won't eat through most plastic, but will evaporate and increase in concentration so you want to keep it sealed if possible. Just add more distilled water if it does evaporate. Mark the level on the inside of the container with a permanent marker for reference.

Dilute with lots of water and/or use baking soda to neutralize it before disposal.  

I use almost exactly the same process. The only thing different is I like my acid bath cold. Anywhere from 45-60F is my happy place. Instead of a battery charger I use a regulated power supply and set it at 5.8-6.0 amps for 60 minutes. You'll want to slightly adjust your time based on on surface finish. I've noticed that a glass-bead blasted lower (smooth) takes about 17v to reach 6 amps but a 70-grit AO-blasted lower will hit 6 amps at around 12-13v (more surface area).

PS - I do not use an air-stone in the acid bath as I have been told it will dissolve and contaminate the bath. I just use an open vinyl tube with no diffuser. Make sure your agitation-air does not contact the work piece.  

Good information... I hadn't heard that an air stone would/could contaminate the bath. The stone finally broke after a year or so. Now you mention it, there would be minerals in the stone the H2SO4 could chemically upon. I'll figure out something else for next time.

I understand Type 3 uses lower temps and more juice as your process seems to lean towards. Sounds like you have a good setup.

You too!

Regarding temp, One of the primary reasons I like to start with a lower temp is to end with a reasonable temp. Since the tank temp will rise during the process. Working with small tanks (~3 gal) has that disadvantage.

For others here contemplating DIY anodizing, as with many things, prep is critical. Thorough cleaning and degreasing is vital. Rinse well between steps using distilled water, never tap water. Do the math to get your combination of surface area, time, and amperage correct. Ensure solid contact with the hangar wire. Anodize thickness is a bell curve. It builds to a maximum and then if you go too long it starts to reverse and you lose thickness. You can't just eyeball it and get good consistent results. I also recommend getting good dye made for this. You went to all the trouble to assemble an anodizing line; finish off with dye worthy of your efforts.

Regarding maintaining the temperature low, why not use a ice water bath?  A bucket within a bucket so to speak, where the outer bucket contains ice water which will be at a constant 32 deg-F and the inner bucket can be the anodizing solution.  Use big tubs and let it cool for a day or so and your heatup troubles may be reduced.

looks like a really good job OP



I would love to see you do the exact same thing again with the exception of blasting with aluminum oxide prior to anodizing

Your car battery is plastic.......