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Posted: 9/1/2003 8:34:49 PM EDT
How would I go about removing the finish from my AR so that I can refinish it in a new color? I'm open to any and all suggestions. For example if I were to use some sort of sandblasting technique what type of media should I use and how much pressure should be applied? I'm attempting my first upper build from the ground up and if all goes well I have a few people waiting in line for me to build one for them. Thanks.
Link Posted: 9/1/2003 9:11:29 PM EDT
I think my dealer uses bead blasting over sand. If it is parkerized, the Duracoat stuff really works great over top of it and no need to strip it. As to pressures on bead blasting, I am out of my league to answer that.
Link Posted: 9/2/2003 3:48:53 AM EDT
To remove the finish from the aluminum components, including the upper/lower you have to remove the anodization. The anodization process 'grows' a protective coat on the aluminum and the dye is absorbed into the pores of this coating and then locked in during the sealing process. The 2 easiest ways are to bead blast or to put in a lye solution to disolve the anodization. In either case, the part will have to be re-anodized and either re-dyed or coated/painted.
Link Posted: 9/2/2003 6:35:04 AM EDT
Explain the process of re-anodizing the metal. Thanks.
Link Posted: 9/2/2003 6:52:56 AM EDT
[Last Edit: 9/2/2003 6:53:28 AM EDT by fizassist]
If you search for "home anodizing" on Google, you can find references for DIY setups. Some places, like [url=http://www.caswellplating.com/kits/aluminum.htm]Caswell[/url], sell complete setups running a few hundred bucks. I've considered trying anodizing, but I've heard it takes a lot of set-up and it's difficult to get a good, solid finish. I may give it a shot when I move to a bigger place and have a dedicated workroom.
Link Posted: 9/2/2003 7:12:48 AM EDT
Don't use lye. Get a special anodizing stripper from a place like Caswell's. Its made to eat the aluminum oxide but not so much the aluminum itself. If you leave your part in lye chances are it will change the dimensions. You can anodize yourself at low cost, but you should pick up a few of the chemicals like dye and sealer from, again, a hobby plating shop like Caswell's or some other outfit.
Link Posted: 9/2/2003 7:22:21 AM EDT
Do a google search for anodizing and you will get many "hits". I have downloaded some of the instructions and they are simple to follow and understand. The materials appear to be easy to obtain also. I plan on buying some aluminum stock to practice on many times before doing the real thing. That way I don't foul up my one good piece. Good luck on your project.
Link Posted: 9/2/2003 8:04:54 AM EDT
So how about this. Can I remove the finish from the upper without hurting the anodizing? If so how would I go about doing it? Thanks for all your help so far.
Link Posted: 9/2/2003 9:14:11 AM EDT
No. The anodizing is the finish.
Link Posted: 9/2/2003 9:54:10 AM EDT
Most of the information on the net is 'misleading' and contradictory. Even Caswell's information is incomplete in some instances, although the products they sell work very well. Lye works fine if your careful, but as stated Caswell is easier to use. Doing the anodization and re-dyeing at home will run about $200-300 for a regulated power supply, acid, dye and other chemicals & supplies and really isn't worth it unless you are going to do more than a couple items. Don't believe the battery charger, car battery methods found on the net. They work in some cases and some people have had success, but more people have failed than succeeded using these methods. You can't separate the anodization and the dye. Removing one results in the other being removed as the dye is in the pores of the anodization. If you are looking for a cheap/home solution, then either Brownells or Norrells Moly Coatings work well. If you are looking for a quality job, then it is best to send it out to be re-anodized & dyed. It depends on what results you are looking for and how comfortable you are dealing with acids and electricity and how much you can tolerate ruining the part.
Link Posted: 9/2/2003 11:38:00 AM EDT
So if my plan was to re-finish the rifle in one of Norrell's Moly Resins would anodizing the metal even be necessary? In this case wouldn't I just be able to remove the original anodized finish and apply the Moly Resin to the bare metal? I realize you can apply Moly Resin over the existing finish but Norrell recommends for the absolute best finish to apply it on bead blasted metal. Also I'm concerned about the finish being too thick with both the anodizing and Moly Resin being applied. If I'm being crazy someone please let me know. Thanks.
Link Posted: 9/2/2003 3:54:58 PM EDT
I've used both a battery charger and a dc power supplie and have not noticed a difference between the two.
Link Posted: 9/2/2003 4:24:14 PM EDT
Originally Posted By 00_buckshot: So if my plan was to re-finish the rifle in one of Norrell's Moly Resins would anodizing the metal even be necessary?
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No
In this case wouldn't I just be able to remove the original anodized finish and apply the Moly Resin to the bare metal?
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You don't seem to know what anodization is. Anodization is not the finish. It is the hard, protective cover made of aluminum oxide that grows out of aluminum when it is subjected to an electrical charge in the presence of an electrolytic solution (acid), or left in open air for a very long time. It is very hard (aluminum oxide is what some sandpaper is made of) and protects the very soft raw aluminum from dents, scratches and wear. If the anodization is removed, it should be re-treated to restore the protective qualities.
I realize you can apply Moly Resin over the existing finish but Norrell recommends for the absolute best finish to apply it on bead blasted metal.
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I believe that they don't recommend bead blasting, but sand blasting in cases where you are working with bare/raw metals. Applying it over blueing/phosphate results in a very nice finish. The only thing they recommend if you are applying it over another finish is that you make sure that the base finish is in good condition and that it is securely bonded to the metal otherwise the base finish may separate which will take off the moly coat too.
Also I'm concerned about the finish being too thick with both the anodizing and Moly Resin being applied.
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As previously explained you shouldn't remove the anodized surface. The Moly goes on with an airbrush, so it is very thin and won't affect the dimensions to any great extent, unless you put it on too thick.
If I'm being crazy someone please let me know. Thanks.
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Not crazy, but you have a lot of research to do before you decide what you want to do. As suggested, you should do a search on anodization to get an idea of exactly what it is if you are intent on removing the existing anodization and dye from the aluminum parts. If you're just going to overspray things with Moly, then make sure you read the instructions and follow them precisely. The color, gloss and flexibility of Moly is affected by the pre-treating temp and the baking temps. If you are expecting to use the moly (or any finish) to match colors between parts, you are in for a lot of work. They can come very close out of the bottle, but you won't get a 100% match without repeated attempts, adjusting temps, coverage and making color, tone and gloss adjustments. If you tell us exactly what you are looking for and what parts you are planning on re-finishing we may be able to provide additional suggestions.
Link Posted: 9/2/2003 4:46:46 PM EDT
Originally Posted By NevadaARshooter: I've used both a battery charger and a dc power supplie and have not noticed a difference between the two.
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You have been either lucky, or the differences haven't manifested themselves yet. The problem with the battery charger method is that you cannot control the amperage and the voltage is usually insufficient. Ideally, the voltage should be in the 20 vdc range and the amperage should stay constant in the 3 amp range. Most of the stuff on the net tells you to figure the area of the part to be anodized to determine the amount of time required. This is only an approximation. The problem with this method is that if the time is too short, the growth of the anodized surface doesn't reach the maximum thickness. If the time is too long, the acid in the electrolyte actually begins to dissolve the coat you just grew. It is possible to detect this if you use an ohm meter and check continuity between 2 locations on the part although it is a pain in the ass. Removing the part from the electrolyte and drying it completely and periodically checking continuity will show an increase in resistance during the anodization process. (Raw aluminum conducts electricity, aluminum oxide does not). As the aluminum oxide grows, resistance increases, but if it is kept in the acid too long, you will actually see the resistance drop as the acid eats away at the aluminum oxide. A poor anodization usually manifests itself in poor absorption of the dye with splotches, uneven color or even failure to accept the dye. Sometimes the pores are too small to accept the dye, sometimes they are partially dissolved (or haven't grown enough to accept the dye). If you apply an external coating such as Brownells or Norrells are not absorbed into the pores of the anodized shell but lay on its surface. A less than optimum jacket of aluminum oxide will be present and will provide a protective hard coat, but it won't be as thick as it could be. Using the Regulated DC Power supply, you set it for 3amp Constant Current Mode (for a AR15 lower) and let it draw whatever voltage it requires (probably 17-20vdc). The voltage will continue to climb as anodization progresses as the power supply tries to overcome the resistance being built up on the part. When the process draws the maximum voltage and voltage begins to drop is when the process is complete and you have the thickest anodization layer. By watching for this voltage drop, you can detect when the process is complete and avoid the situation when the acid begins to eat away the surface you just produced.
Link Posted: 9/2/2003 4:48:20 PM EDT
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