Has anyone used a caustic soda bath (NaOH) in lieu of a bead blast before anodizing their lower? I figure a dip in NaOH, followed by a demux would be a good way to get a clean matte surface prior to Anodizing and eventual Cerakoting.

Or maybe just skip the Cerakote after anodizing for my beater / T&E lower.

The NaOH bath doesn't do nearly as well as a bead blast job. I found that the lye bath on smooth 6061 leaves a sort of uneven satin finish - not nearly as even. Nor as matte as I get if I bead blast first. I prefer now to blast, lye bath, desmut, then anodize.

Well the issue for me is that I do not have access to a blaster. Actually I do but it's 4 hours away and I have to pass through some not-so-friendly states to get there.

Do you think a lye bath would be fine on a 7075 lower if in the end it would be dyed black and Cerakoted? FWIW I wanted to use the lye bath as a way to prep the surface for the Cerakote.

Thanks

Without access to a blaster, what I'd do is buy a box full of those Scotchbrite-like buffing wheels for my Dremel tool and go after it. That way you can get into all the nooks and crannies, and with some care I think you'd end up with a nice, consistent finish. Toss the finished product in the lye bath (or not, if you're Cerokoting without anodizing.) The lye bath is primarily to remove aluminum oxide from the part so the anodizing process can get started - I'm not sure that it really would create enough "tooth" for a spray finish to grab onto.

You mentioned that you have to travel a long ways to get access to a sand blaster. Recognizing that, but not really knowing your situation - could you use something like this? Harbor Freight hopper blaster  If you have access to an air compressor and a big cardboard box, for $20 you could probably get the job done.

I have a "pancake" compressor, 150psi, 6 gallon Porta Cable that I use for small projects around the house would this be big enough? I really don't mind waiting for it to refill between blasts. Any input on what size and type of blast media I would need?

Also that gun looks pretty cheap any thoughts on if this would even work? I don't have space in my garage (Thanks to my wife and her stuff) but I have plenty of room in the basement to setup a small cardboard booth.

But yeah, I'm going to anodize and dye regardless of if they get Cerakoted or not.

Thanks Again!

You're right - the gun is pretty cheap. I have a Harbor Freight benchtop blast cabinet, and it was also pretty cheap - but it did a sufficient job for a long time. After blasting several FN-FAL builds and a few AR lowers, I rebuilt it using some higher quality valves, etc. I need to scrap it or rebuild it again now.

That little handheld blaster will take awhile to get the job done, but if you're patient, I think you could make it work. Keep in mind that since it's being used out in the open, it will create a lot of dust. One possible way to prevent that is to build a makeshift blast cabinet out of a big cardboard box with a clear plastic sheet over the front (even just clear Visqueen). Then, cut a hole and stick a shop-vac nozzle in the box to suck up and contain the dust. Otherwise, you'll have grit over everything in the basement, including your wife's stuff. Which would cut short your gunsmithing activities, I'm sure!

Your little pancake compressor will be slow, but will accomplish what you need eventually. I have a large, single-stage 40 gallon Craftsman compressor, and I still have to wait for it to catch up.

Regarding the grit, I've been using a blend of glass beads with aluminum oxide - thought I got if from Harbor Freight, maybe not. I don't recall the exact grade, but I think it's around 120-180. The blend seems to work pretty well in keeping the alox from getting too aggressive and rounding off engraving or sharp edges. I've been happy with the result - it leaves a nice matte/satin finish that takes anodizing well and hides any minor surface blemishes. Hopefully you'll get some other recommendations from other members.

Thanks! I'm going to out later tonight and pick up the gun and a big clear Tupperware container to use as a blast booth, with some modifications of course.

Yeah she is already pissed at me for milling my lower too lose to the clothes drier. Apparently she was picking aluminum bits out of her shirt at work last week.

I'll report back here with updates after I get started.

I use a pancake compressor with the HF media blast gun. Works fine. I added a water trap to the hose prior to the gun just to keep moisture out of the media and blast at 40psi to 60 psi. This is on a bare lower. To knock off Gunkote I had to take the pressure up to 80 psi and use short bursts.

Use120 gr Al Oxide as media. My blast cabinet is a storage box with a clear plastic window siliconed on top.  Added 2 holes to fit short pieces 4" drainage pipes and taped long blasting gloves from HF to them. Added a breather hole with some PVC pipe and rubber band a throw a rag over the end to reduce the dust.

Added a 24" led work light to the inside of the box so the part to be blasted can be seen easier. Added another hole to run the power to the light and the compressor hose into the box and sealed the hole. Wear a mask because dust still escapes from the box.

You doen't need to blast before anodizing. The NaOH bath is a standard step in anodizing and I've Gunkote over anodize without blasting, but it did stick better when blasted.