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 Sandblasting Question
SandyShoes08  [Team Member]
1/12/2009 4:12:33 PM
I have a lower receiver that is grey and I want to paint it black. My friend has a sand blasting setup, the box and air tools and all that, but he says he only has sand and sand is too coarse. He says aluminum oxide is the best material to blast with and a friend of his has access to one at work and is willing to blast my lower for me.

I trust my friend, but I'm a little apprehensive about giving this pre-ban lower (in CT it matters) to a friend of a friend and having it blasted with some substance that sounds like a chemical I've never heard of.

Is sandblasting with aluminum oxide really that much better than roughing it up with a bit of fine grit sand paper? What grit sand paper should I use, or should I go with the aluminum oxide blasting?
SandyShoes08  [Team Member]
1/12/2009 4:38:45 PM
I found another post where someone said DuraCoat recommends 600 grit sand paper, so I'm going to try that.
patriot_performance  [Member]
1/12/2009 4:57:57 PM
At my shop we do power coating. I have a cabinet setup with glass beads. They are more expensive than aluminum oxide or black beauty like most shops use. However it will leave you a very fine consistent finish, much like 600 grit sand paper. It comes in different grit sizes much like other abrasives. Would give your rifle a perfect foundation for all kinds of coating options.
NUcadet07  [Team Member]
1/12/2009 5:06:41 PM
Originally Posted By patriot_performance:
At my shop we do power coating. I have a cabinet setup with glass beads. They are more expensive than aluminum oxide or black beauty like most shops use. However it will leave you a very fine consistent finish, much like 600 grit sand paper. It comes in different grit sizes much like other abrasives. Would give your rifle a perfect foundation for all kinds of coating options.


Absolutely do NOT use glass bead! It will not give you're lower enough grit to get a good finish from the Duracoat. I refinished all my pre ban lowers with Moly Resin before I duracoat. Duracoat is fun stuff but it is far from a permanent finish. My moly resin has held up to tons of abuse on my AR's and still looks realtively new three years later. The duracoated guns wear much faster. I recoment having your buddy blast it with alum oxide and then use moly resin. If you want, I see you are local. If you feel like taking a trip to Bridgeport, get it blasted then come pay me a visit and I'll get you all squared away with the Moly Resin. I'm always willing to help out another CT shooter.

Steve
Colt45guy  [Team Member]
1/13/2009 7:53:26 AM
I prefer Brownell's GunKote myself......Brownell's Teflon/Moly is a close second and has a different selection of colors.



Moly, Teflon/Moly, WonderCoat/Kote––––they all work very well when they're prepped correctly.....I like the Brownells 'Kote' products because they come in rattle cans, and there's no mixing or crazy long cure times. (I've never heard of the Moly Resin.....I need to look into that) But I'll second the advice to use al ox instead of glass beads.

The whole point of abrasive blasting is to give the surface as many sharp cuts and crevasses for the paint to adhere to as possible......the smooth glass beads only peen little smooth dimples. It gives more surface area, so it'll take a bit more paint, but it's not much better than painting a polished surface when it comes to adhesion. It will scratch, flake, and chip much more easily without those sharp edges, nooks and crannies.



If you don't believe me, try this experiment––-blast one side of a piece of metal with al ox and the other with glass beads. Give it a coat of Krylon and let it dry. Take a green scotchbrite pad and vigorously scrub each side.....which side has the most paint left on it? The al ox side will have the better adhesion, and that's what we're looking for, right?


Glass beads are only used in my shop to frost stainless steel or to prep for a surface conversion finish like bluing. Come to think of it, I learned about the differences in the finish prep while working on a stainless 1911 many, many moons ago. I used some al ox to matte the slide, and found out that it became a royal PITA to clean after firing. I ended up sanding it smooth and re-blasting with glass beads. To the naked eye, it looked like the same matte finish, but the clean up after the glass bead blast was a simple wipe down with an oily rag instead of requiring a carb cleaner blast and lots of elbow grease to remove the carbon.







As far as your idea to use 600 grit sandpaper, yes it'll work––but it's really hard to get complete coverage around all the shapes. An abrasive blast takes all of 10 minutes, and you will get much more complete and even coverage.
GreenLantern  [Member]
1/14/2009 11:01:21 PM
I'm not sure why you'd need to blast it unless it was one that was maybe teflon coated. I've Moly-Resd 4 upper/lower combos and the only prep I did was to degrease. No problems with the stuff sticking after curing.
j_king  [Member]
1/17/2009 6:11:16 PM
Originally Posted By GreenLantern:
I'm not sure why you'd need to blast it unless it was one that was maybe teflon coated. I've Moly-Resd 4 upper/lower combos and the only prep I did was to degrease. No problems with the stuff sticking after curing.


No flaking or chipping of the moly resin with no sandblasting prior to application?
USMC223  [Member]
1/18/2009 3:00:26 PM
Aluminum Oxide is the blast media you should go with. As stated above glass beads do leave a nice finsh but not rough enough for a solid base for the paint/resin/ETC.

I did some CerraKote work and they said 180 Aluminum Oxide was the blast media of choice. I had glass beads already and hemmed and hawed about not using Aluminum Oxide. Well I sucked it up and bought some Aluminum Oxide.
The results were well worth it. IMHO.
Long lasting and rugged as hell.
legonas  [Team Member]
1/18/2009 3:02:57 PM
if the lower is anadized no blasting is necessary, just good degreaseing.

park and anadizing are the absolute BEST base for any type of spray on finish.

just degrease THROUGHLY beforehand.
GreenLantern  [Member]
1/20/2009 9:55:58 PM
Originally Posted By j_king:
Originally Posted By GreenLantern:
I'm not sure why you'd need to blast it unless it was one that was maybe teflon coated. I've Moly-Resd 4 upper/lower combos and the only prep I did was to degrease. No problems with the stuff sticking after curing.


No flaking or chipping of the moly resin with no sandblasting prior to application?


Nope, none of it has come off. The instructions even say to verify the curing was sufficient by putting some MEK on a cloth and wipping it across the surface. No color bleed = good.

Moly res is so thin that it wouldn't flake if done improperly. It would probably wear off through contact or via cleaning solvents. Obviously you'd notice that by seeing gray spots as the black wore off.
Yankee_81  [Member]
1/22/2009 10:52:08 AM
+1 on the blasting with aluminum oxide. it is very expensive, but it gives the best surface for the finish to stick to. gunkote recomends either 400 or 600 grit, I cant remember which, but it says right on the bottle.

some people have had good luck using sandpaper instead of blasting as long as you use the K-phos solution(or similar zinc phosphate metal prep solution) before you spray it. it's basicly an acid that microspocicly pits and oxidizes the surface, it provides an excellent surface for the finish to stick to.