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How to polish Anodized Aluminum

Discussion in 'The Hokey Ass Message Board' started by Abomination, Dec 28, 2006.

  1. Abomination
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    Abomination Member

    I saw this today, posted in the 1963 & 64 Cadillac Community:
    http://groups.msn.com/196364CadillacCommunity/the63and64cadillacclub.msnw

    I figured it would be of interest, and am passing it on.

    ~Jason

    According to GaryAllan:

    "After a recent post about how to polish the grill, I went back into eBay and found the seller of a 1963 grill that was indeed highly shiny and polished. I emailed the seller and he was kind enough to email me back. I did some research into what he told me and it is so simple.

    The anodized aluminum will never gleem and shine like chrome if it has turned dull. That is what anodizing is suppose to do, protect the aluminum underneath it. The more polish etc. you use the more the anodizing will work to protect the underneath.

    The web site I found for polishing anodized aluminum is http://www.secondchancegarage.com/public/665 . The instructions are to remove the anodizing, polish the aluminum to a high shine, then seal the aluminum with a clear polish, clear coat or like someone did, a clear powder coat. To paraphrase what they said to do:

    To remove the anodizing, take the aluminum part and soak it in a mixture of water and DRAINO drain cleaner. (Sodium hydroxide is the chemical). They recommend a mix of 1 tablespoon Draino to one gallon of water. Take the part, soak it in the mix so it is completely covered. Make certain there is plenty of fresh air, the fumes are toxic.

    They say there will be bubbles forming on the aluminum surface and on the water mix, take the part out of the mix and gently shake the "smut", the chemical residue, off the piece. Keep checking the piece every minute or so and keep removing the smut until you have a completely clean surface.

    They say if it going too slow, you can add more drain cleaner. There should be a flat uniform color, stains and blemishes should have disappeared leaving just scratches. Rinse thoroughly with fresh water. Any dark spots may be residual smut and needs to be removed by further treatment.

    Rinse, and rub clean and dry.

    Sand with 800 grit paper to remove scratches to take it to a bright shine. Once as shiny as desired, I hope someone else here can add about how to sand because*I have not done it, protect the piece with waxing or some type of clear coating.

    I bought an extra grill for my 63 and will try this later in the Spring when I can do it outside. No recommendations were given as how to dispose of this chemical soup once you have done it. Any ideas would be appreciated.
    I would not send down the drain into a septic tank, maybe the municipal sewer system would handle it ok. After all, some places have some pipe that is aluminum and people do use draino to clean drains.

    I also went to google and searched how bikers clean and polish aluminum on bikes because they have many parts highly polished aluminum and found the same advice.

    Gary

    If anyone does this process, please let us all know by posting it on the board.


    From: ogaribay37
    great post, as for the junk left over let it dry, then it is no longer toxic, and throw it away in garbage."
  2. fergenboysinc
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    fergenboysinc Member

    Sounds to easy! Thanks for posting it. I will give it a try later today.
  3. skajaquada
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    skajaquada Member

    just a warning, be VERY careful with the sodium hydroxide. it's not in as concentrated a form in drano as when you buy it in crystal form but it's still something to look out for. the fumes can knock you on your ass so make sure you're well ventilated or have a good respirator that's rated for chlorine and acids and also make sure you have nitrile, NOT latex gloves when working with it. i work with this stuff on a daily basis in its crystal form and can vouch firsthand on the dangers of it..ask some of my guys who didn't listen to me!:rolleyes: does sounds like a great way to remove that grime though...i'll have to give it a try sometime.
  4. crowerglide
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    crowerglide Member

    If you want to strip the anodizing, take it to the plating shop. They can put it in the tank and remove the anodizing, sometimes in just a few minutes. (I think they simply reverse the anodes.) Then you don't have to fool with all the caustic/toxic home-brew chemicals and fumes. Polish it and then have it clear (or color) anodized if you want a shiny finish. It will only have as good a finish as the polish job you put on it before plating.
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  5. Richard D
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    Richard D Member

    Easy-Off Oven Cleaner works too. Just don't soak too long!
  6. fflood
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    fflood Member

    I know this is a bit off topic from what you were discussing, but the parts could always be sanded polished and re-anodized if need be. Below is a discription of anodizing. This setup is simple to make as long as you are careful with the chemicals and electrical current.

    I know that some aluminum parts are too large for the following procedure, but this works great for small parts. I have set up my own anodizing setup from scratch and it is quite easy to do. Polished parts will retain their shine if they are anodized and sealed (so it's the same process of anodization, but no die is introduced and the part is simply sealed). This eliminates the sealed in paint look if that is a problem for some.

    My setup is:
    A series of small "brute" containers for the various baths. One large grey "brute" container (think: industrial trash can) that contains the sulpuric bath. This container has two copper rods on either side of it that lead sheet is suspended by. In the center of the bucket is an aluminum bar with holes drilled in it and bolts to tighten down against the hangers that suspend the parts. The hangers are made from aluminum tig welding rod of various sizes. The copper rods are attached to the negative terminal of the rectifier and the center bar that your workpiece connects to is connected to the positive side of your rectifier. I have more info on this process, as I teach this in my Metals class at a university. I can also send pics of the setup if anyone is interested.

    Anodized and Dyed Aluminum

    Process and benefits
    Aluminum anodizing is an electrochemical means of converting aluminum hydroxide (a passive state of aluminum) to aluminum oxide (a reactive state of aluminum). Anodizing changes the physical and chemical characteristics of the aluminum surface by creating an anodic film that is highly porous in nature, thus allowing the aluminum to be decoratively colored by absorbing dye into the anodic film. The anodizing process also renders the surface harder and more abrasion resistant, insulates the aluminum surface against the passage of electricity, and helps improve upon the natural corrosion resistance of aluminum.

    Alloy Selection
    In the design of pieces to be finished by anodizing and dyeing, the selection of the aluminum alloy should receive careful consideration. The amount and type of alloying constituents has a pronounced effect upon the porosity, clarity, and hardness of the anodic film and thus, upon the appearance of the finished aluminum part. 1000 series high purity alloys are particularly well suited for “bright finishing” applications since they produce exceptionally clear anodic oxides. Other desirable alloys include 5000 and 6000 series which contain magnesium and magnesium-silicide respectively. Special formulations of these, such as 5657 and 6463, are outstanding in brightness retention. 1100, 5052, and 6061 alloys are also desirable and are readily available as surplus. The 2000 and 7000 heat treatable series are not ideal as the anodic films on the alloys almost always exhibit minute discontinuities and are subject to corrosion pitting.

    Dyeing
    Dyeing of the anodized aluminum part is a relatively simple process. Dyeing is performed before sealing as the pores of the aluminum anodic film are open and receptive to dye. The anhydrous form of the aluminum oxide film links with dyes more easily, which the monohydrate form that the oxide becomes after sealing, will not do. After neutralizing the piece, it should be rinsed and then immediately placed into the dye. Do not allow the piece to dry out after neutralizing. The dye solutions consist of from 0.1 to 10 grams/liter of the proper dyestuff dissolved in water (mix according to manufacturer_s instructions). Most dyes require approximately 2 grams/liter of water. Dye baths may be heated with an immersion heater or on hot plates (100°-120°F/37°-48°C) to produce darker shades. Dye baths used cold will produce pale tints. Generally, aluminum parts are suspended in dye baths for 5-10 minutes and checked frequently. Once dyed, the aluminum piece is rinsed well and ready for sealing.

    Dyeing Variations
    Multicolor selective dyeing of an anodized surface is possible. The object is first completely, or partially anodized. A selected area is protected with a masking resist that is capable of remaining intact on the aluminum surface and withstanding the dye bath temperature. Adjoining color dyeing is possible when a resist is applied to a selected area of the anodized aluminum part, the exposed area is dyed. A second application of a resist can then be applied to protect the already dyed area, areas previously protected by the resist are then exposed to a second dye bath. Over-dyeing of a color with a second color, covering the first completely or partially, is also possible.

    Sealing
    Once the pores of an aluminum anodic film are sealed (the final step in a normal production process), the film acts to protect the base metal and minimizes its corrosion, streaking, and discoloration by shielding it from atmospheric contact. Proper sealing of the dyed anodic film is essential in eliminating film porosity and in making the surface resistant to further dyeing, fading, staining, and corrosion. The sealing process converts the amorphous aluminum oxide anodized film to aluminum monohydrate, which has a greater molecular volume. This increase in volume causes the pore walls to swell and close so that the dye is locked in. The appearance of the dye film is not changed in the process. Commercial sealers, hydrolizable metal salts incorporating nickel acetate (and sometimes cobalt), are available and should be mixed according to the manufacturer_s instructions. The sealing salt is brought to boiling and the dyed part is immersed for approximately 10 minutes.
    Once the piece is sealed, it is rinsed thoroughly in water and allowed to air dry or is pat dried with a soft clean cloth.
    Often, there is a cloudy film left on the surface by the sealing salt. This can easily be removed by lightly scrubbing the piece with a toothbrush and soap, or with 0000 steel wool and soap.

    Safety
    Fumes are generated during the caustic soda etch, anodizing, dyeing, and sealing processes. Hydrogen gas is given off during the sulphuric acid bath portion of the process. This is highly flammable (see Hindenburg)!! The work area must be well ventilated. Additionally, as with any electrical situation, normal precautions must be observed. Never touch the anode (aluminum part) and cathode (lead sheet/bars) or connecting rods and wires while the rectifier is on. The current generated is extremely dangerous. Rubber gloves should be worn to insulate against electric shock and also for protection from acid and caustic soda baths. Rubberized lab coats or lab aprons will provide protection from splashed acids and chemicals.

    Procedure numbered/Supplies and Equipment listed after:
    1. Clean aluminum parts to be anodized.
    Degrease with pumice (optional).

    protective clothing (including rubber gloves)
    pumice

    2. Suspend parts on aluminum welding rods. Fit should be secure and tight.
    aluminum
    aluminum welding rod

    3. Caustic soda etch 10 minutes.

    Drano or TSP mixed with water

    4. Rinse.

    distilled H2O

    5. Nitric acid etch 2 minutes.

    water and nitric acid 50/50

    6. Rinse.

    You may put the chemicals in polyethylene food service containers with lids

    7. Anodize in a sulfuric acid bath at 12 volts for 15 minutes to 1 hour. Longer anodizing times produce larger pores ‹ the aluminum will accept dye more freely resulting in intense color.

    8. Rinse.

    distilled H2O

    rectifier (supplying 20 volts and 10 amps) a battery charger may be used in place of the rectifier, but there is less adjustability.

    cathodes (lead sheet)
    sulfuric acid and distilled H2O 30% solution

    9. Neutralize in baking soda and water. Longer neutralizing times result in more even color.

    10. Rinse.

    11. Dye. For maximum saturation, dye bath should be heated to 100°-120°F. If you wish to seal a polished surface then no die is needed (jump ahead to sealing)

    12. Rinse.

    thermometers (measuring 150°F)
    hot plate or immersion heaters
    dyes (Sandoz aluminum dyes) RIT die may be used as well, but color may bleach out over time due to exposure to sunlight.

    13. Seal for 10 minutes in boiling solution.

    sealing salt (Sandoz) or boiling in distilled H2O for 30 minutes
    electric slow cooker

    14. Rinse.

    15. Pat dry with soft clean cloth.

    16. Scrub lightly if needed to remove film.

    Dish soap and toothbrush
    or 0000 steel wool
  7. Richard D
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    Richard D Member

    This is great info! How about a TECH article showing how you built it, and the process of a part being anodized?

    Does highly polished aluminum have the same luster if you clear anodize it? I have some polished aluminum wheels, but they are partly made of steel. I wonder what it would do to the steel if I clear anodized them?
  8. fflood
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    Milwaukee

    fflood Member

    You don't want to put anything but aluminum or titanium (ti makes great hanging racks for supending parts) in the sulphuric bath-so no steel. The sulphuric will attack the steel as soon as you put it in.

    I hope the info helps those do it yourselfers. I know I have learned a ton from hanging out here-I'd be more than happy to return the favor. I will see what I can do about the tech article after the holidays.
  9. Abomination
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    Abomination Member

    Thanks for the safety info - nice to have some from someone who messes with this stuff firsthand!

    ~Jason

  10. Abomination
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    Abomination Member

    You know, that's a damned good idea! I'll bet the heinous chemicals swirling in those tanks would take it right off, but for how much? You wouldn't think it would be TOO expensive...

    ~Jason

  11. Abomination
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    Abomination Member

    This is totally on-topic! I agree with Richard_D on this one - post some pictures inline with the text and you'll have a great tech article.

    Besides, HAMBers love this kind of stuff. We also love pictures (for those of us who can't read). :)

    Jeez man, you ROCK!

    ~Jason


  12. porknbeaner
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    porknbeaner Member

    Good tech.
    That part about the fumes should also note that more than toxic it is explosive. Draino + Aluminum = Hydrogen

    Just thought I'd throw that out there, I know that most of you don't smoke. :D
  13. gashog
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    gashog Member

    I read in a restoration magazine that if you coat a dull anodized part in wheel bearing grease and let it sit for several weeks, you can polish it to near original luster with an old cotton tee shirt. Several applications are required for best results. The advantage of this technique is that it does NOT remove the annodize, just brighten the finish. I have never tried this and would be curious to see if anyone has any luck with it.
  14. fergenboysinc
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    fergenboysinc Member

    Do you know how long I should soak the part. Its been 5min. and nothing. And to be clear I got Drano clog remover. there was no plain drano. And I see you are spelling it different???? Do I have the wrong stuff?
  15. skajaquada
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    skajaquada Member

    if you want the pure sodium hydroxide, go to a plumbing supply place and buy some "thrift drain cleaner" for around $12/lb. it's PURE sodium hydroxide crystals so start out with maybe 1/2tsp per gallon. dissolve it in warm water in a well rinsed milk jug or something made of GOOD plastic. even better is if you have a spare muriatic acid jug that you've rinsed out with a baking soda solution and flushed VERY well with clean water. just be careful though, this stuff is WICKED in its crystal form. plus, it cleans drains like a motherfucker...just don't stand with your face over the drain when you put it in;)
  16. polisher
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    polisher Alliance Vendor

    just as well you haven't tried it.
    It doesn't work.
  17. polisher
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    polisher Alliance Vendor

    Sodium Hydroxide( Lye) can be purchased from any hardware store.
    Has nothing to do with chlorine.
    Respirators should still be used if in poorly ventilated areas.
    Fume is explosive, but will dissipate.
    The waste is not controlled and can be dumped as it is alkaline.

    Nitric acid is controlled.
    Anybody that messes with nitric acid using rubber gloves or nitrile gloves is an idiot.
    Nitric should be kept in passivated Stainless steel tanks only.
    The tanks it is shipped in are 15 gallon tanks and cost over $250 per tank.
    Gloves must be neoprene.
    It should only be kept by registered businesses and labs that use nitric.
    HDPE tanks are not good enough to store nitric in.
    Tupperware certainly would create some interest.
    They say there's them that know and them that teach.
  18. polisher
    Joined:
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    Belfast,Maine, U.S.A.

    polisher Alliance Vendor

    Sodium Hydroxide( Lye) can be purchased from any hardware store.
    Has nothing to do with chlorine.
    Respirators should still be used if in poorly ventilated areas.
    Fume is explosive, but will dissipate.
    The waste is not controlled and can be dumped as it is alkaline.

    Nitric acid is controlled.
    Anybody that messes with nitric acid using rubber gloves or nitrile gloves is an idiot.
    Nitric should be kept in passivated Stainless steel tanks only.
    The tanks it is shipped in are 15 gallon tanks and cost over $250 per tank.
    Gloves must be neoprene.
    It should only be kept by registered businesses and labs that use nitric.
    HDPE tanks are not good enough to store nitric in.
    Tupperware certainly would create some interest.
    They say there's them that know and them that teach.
    The waste from sulphuric and nitric acid has to have a pH of 5 or higher before it can be dumped.
    Regular refuse and transfer stations will not take liquid acid solutions.
    Clean Harbours will at $550 to $600 per 55 gallon barrel or part of.

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