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  1. #1
    Senior Member JonnyHK's Avatar
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    clear coat on polished groupset parts?

    I thought that with all the knowledge on clear coats displayed in recent posts that my question might be best answered here.

    I have purchased cheaply a full groupset (DA 7700) for my project bike, but the cranks have a well loved look to them.

    I thought that I could polish them, but have realised that there is a clear coat of some sort over the metal. This coating would be sanded off before polishing.

    Once polished, I won't have a protective coat. How much of a problem will this be with the alloys used to make cranks? Will I have to re-polish often? Will a standard cleaning product (ie alloy polish, car wheel type?) be ok? Should I get a clear coat put on the newly polished metal (I can get two part polyurethane done easily at my work)?

  2. #2
    Older I get, Better I was velonomad's Avatar
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    I haven't had much luck with clear coats. It looks great for a few months then it gets milky looking as the aluminum begins oxidizing again. Still looks good, just doesn't have that chrome look. I use PPG 2042.

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    Randomhead
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    polished aluminum will dull over time. Just polish it again. A highly polished surface tends to corrode more slowly, all else being equal.

  4. #4
    Insane Bicycle Mechanic Jeff Wills's Avatar
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    Quote Originally Posted by JonnyHK View Post
    Once polished, I won't have a protective coat. How much of a problem will this be with the alloys used to make cranks? Will I have to re-polish often? Will a standard cleaning product (ie alloy polish, car wheel type?) be ok? Should I get a clear coat put on the newly polished metal (I can get two part polyurethane done easily at my work)?
    Polish is easy to maintain, and it won't show wear as easily as a clear coat. Cranks lead a tough life, though, so you can expect to re-polish them periodically (interval depends on your pickiness).

    I have a polished aluminum frame, rear hub, and crankset. The frame stays pretty nice, but the cranks get beat up. I use Mother's Mag and Aluminum polish to keep 'em shiny:
    http://home.comcast.net/~jeff_wills/jeff-grr/index.htm
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  5. #5
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    The cranks don't just have a clearcoat, they're anodized. This is a frequent topic on the forum, and generally a bad idea. Anodizing is a chemical process which makes the surface non reactive, so you don't have to polish them and it won't pit. It's considered to be desirable.

    Anodizing is not easy to remove, nor should it be. To each their own though!

    Use Brasso to polish Al.

  6. #6
    Senior Member JonnyHK's Avatar
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    Quote Originally Posted by Garthr View Post
    The cranks don't just have a clearcoat, they're anodized. This is a frequent topic on the forum, and generally a bad idea. Anodizing is a chemical process which makes the surface non reactive, so you don't have to polish them and it won't pit. It's considered to be desirable.

    Anodizing is not easy to remove, nor should it be. To each their own though!

    Use Brasso to polish Al.
    I don't have a pic, but they are not anodized. Most certainly a clear coat of some type. Much of the wear damage that looks so bad is small chips and cracks in the surface coating that have dirt or oxidation in them.

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    Senior Member Nessism's Avatar
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    Quote Originally Posted by JonnyHK View Post
    I don't have a pic, but they are not anodized. Most certainly a clear coat of some type. Much of the wear damage that looks so bad is small chips and cracks in the surface coating that have dirt or oxidation in them.
    The stock 7700 parts ARE anodized, clear anodized. Easy Off oven cleaner with lye will remove the anodizing if you choose to go that way.
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  8. #8
    Senior Member JonnyHK's Avatar
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    Quote Originally Posted by Nessism View Post
    The stock 7700 parts ARE anodized, clear anodized. Easy Off oven cleaner with lye will remove the anodizing if you choose to go that way.
    I've never seen (or heard of) clear anodizing and the cranks certainly *look* like metal with a clear coat. Scratches in the coloured anodizing that I'm familiar with don't look like the wear that is on these cranks.

    Without arguing about the finish of the 7700 cranks (you guys are normally 100% right in this forum, but I keep looking at these things and I'm not 100% convinced!), I've decided to get them polished at a small shop not far from work. I gave the LH crank arm a quick run past the small polishing wheel at work and the result is a nice shiny near chrome look (what you'd expect from polished alloy).

    I will just have to keep them nice and polished clean in the future without the coating (whatever it is!).

  9. #9
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    Quote Originally Posted by JonnyHK View Post
    I've never seen (or heard of) clear anodizing and the cranks certainly *look* like metal with a clear coat. Scratches in the coloured anodizing that I'm familiar with don't look like the wear that is on these cranks.

    Without arguing about the finish of the 7700 cranks (you guys are normally 100% right in this forum, but I keep looking at these things and I'm not 100% convinced!), I've decided to get them polished at a small shop not far from work. I gave the LH crank arm a quick run past the small polishing wheel at work and the result is a nice shiny near chrome look (what you'd expect from polished alloy).

    I will just have to keep them nice and polished clean in the future without the coating (whatever it is!).

    Yes, no need to argue about what we cannot see! Cranks have been clear anodized since I have been riding as a kid in the 70's. DA cranks certainly were anodized, but as you bought them used, we don't know what may have been done to yours from the previous owner. If they were anodized, metal polishers like Brasso has no effect on them, as the anodized surface has been chemically altered and is non reactive. http://en.wikipedia.org/wiki/Anodizing
    http://www.bikepro.com/products/metals/alum.html . . scroll near the bottom for anodized Al

  10. #10
    Senior Member JonnyHK's Avatar
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    I'll see if I can get a decent photo of the cranks as is showing the worn outer face and the nice clean inner face.

  11. #11
    THE Materials Oracle Falanx's Avatar
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    [QUOTE=JonnyHK;9134714]I've never seen (or heard of) clear anodizing and the cranks certainly *look* like metal with a clear coat. Scratches in the coloured anodizing that I'm familiar with don't look like the wear that is on these cranks.

    QUOTE]

    Just for future reference, Jonny, all anodizing is clear and transparent. Any you've seen on aluminium, titanium or magnesium (or stainles stell for that matter) that doesn't look clear is simply due to birefringence events from grain boundaries - in much that smae way a big, single crystal of a 'white' mineral is transparent, but a heavily polycrystalline sample of the same appears that white.

    Aluminium oxide - pure aluminium oxide, which for arguments sake even engineering alloys of aluminum essentially are - is clear and colourless. When you see heavily hard anodised or thick anodised layers of material that don't appear clear it's due to that subtantial diffraction of light from huge, columnar crystals of oxide growing out of the surface. A well anodised and sealed aluminium surface doesn't have to be a thick, obvious one.

    If you first polish a sample, and then anodise it, you'll get the best effect, simply because a very smooth surface doesn't tend to gorw such an irregular and thick coating. Instead it's very dense, thin and smooth itself.

    I hope that helps.
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    I've polished up many older cranksets to look better than new. But I don't think you'll have much luck with clearcoat paint, it will look great for a few weeks then not so much. You could try a commercial powdercoater to put a more durable clear on, it would be harder than paint. Polishing is easy, though messy and time consuming. Lye-based oven cleaner (Easy Off) sprayed liberally and left for an hour will remove the aluminum anodized coating, and will turn the component a mottled ugly industrial gray-black, that's Aluminum Oxide. Don't leave the oven cleaner on too long or you will start to pit the surface. Obviously use rubber gloves and safety goggles, you don't want that crap on your skin. Rinse it well in water, and clean up the soaking container well, lye is no joke despite the fact that you can buy it at Safeway. Then, Mother's Aluminum polish (auto parts store) or any kind of metal polish to clean it up. If it's scratched or dinged up, use a green Scotchbrite pad followed by fine wet sandpaper. Finally, a cotton buffer wheel on an electric drill or dremel tool with some jeweler's rouge wax on the wheel. The more you work at it the more mirror-like it gets. Repolishing later is pretty easy, just a little Mother's polish on a rag to buff it up. The surface should stay polished for awhile depending on how much rain etc you see- salt spray will dull it quickly if you ride near the beach.

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    Quote Originally Posted by JonnyHK View Post
    I've never seen (or heard of) clear anodizing and the cranks certainly *look* like metal with a clear coat. Scratches in the coloured anodizing that I'm familiar with don't look like the wear that is on these cranks.
    I don't know your cranks. I do know that a lot of Shimano parts have been powder coated in silver and a lot are clear anodized. If you check my inane blog you'll see what the silver PC ones look like when they go bad. Bubbles in the finish form and then flake off. Better stuff like D/A got the anodizing.

    The reason you've never seen clear anodizing before is that it is freeking clear. The guys who do it pride themselves on making it look like pure polished metal that never goes bad.

    If you have ever seen a piece of polished aluminum that doesn't turn gray and funky, maybe the screen door or your handlebars you've seen clear anodizing.

  14. #14
    Senior Member Cassave's Avatar
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    Assuming you do strip whatever finish is on the cranks now and bring them to a polish you can always anodize them.

    Find a plater/anodizer in your area. In SoCal, the minumum batch charges run about $40.00, a crankset would qualify for the minimum.

    Any plater in the US will recognize the Military Spec. for anodize.

    Use Mil-A8625 Type II, Class 1 (that's sulphuric, undyed clear)

    You can use the same spec for colored anodize by calling out;

    Mil-A8625 Type II, Class 2 , then specify the color.

    Colored anodize (red, green, blue, gold etc) is achieved by applying an analine dye prior to sealing the anodic layer.
    The dyes are relatively colorfast but all will fade somewhat.

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    Have you found a good shop for this type of project in SoCal?

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    If you try the oven cleaner approach to stripping the old ano you are very likely to severely pit the surface of the metal. I used to have paintball marker parts anodized all the time. If you decide you'd like to have your parts reanodized shoot me a message; I have a number of anodizers who I've used and would highly recommend.

    There really is no substitute for a properly finished part. Most anodizers will strip the existing finish, prep the parts (polish, bead blast, etch, whatever), and reanodize your parts for a pretty reasonable fee.

  17. #17
    Biking Viking. goatalope's Avatar
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    Sorry to resurrect an old thread but...

    I just bought a Dura Ace 7700 crankset on ebay. It looks like crap. I tried to use Mothers Mag Alum polish, but it didn't lather up to a black film like its supposed to, so I believe the cranks must be anodized. I'm interested in trying the Easy Off oven cleaner option to take off the anodizing. Is Easy Off always Lye-based product, or do I need to find a special version?

    Any other advice?
    Tuesdays I work on my hair helmet.

  18. #18
    Aluminium Crusader :-)
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    Quote Originally Posted by goatalope View Post
    Sorry to resurrect an old thread but...

    I just bought a Dura Ace 7700 crankset on ebay. It looks like crap. I tried to use Mothers Mag Alum polish, but it didn't lather up to a black film like its supposed to, so I believe the cranks must be anodized. I'm interested in trying the Easy Off oven cleaner option to take off the anodizing. Is Easy Off always Lye-based product, or do I need to find a special version?

    Any other advice?
    I'm no expert on the exact ingredients of lye, but after some Googling, it seems as though it's just sodium hydrioxide, which is in most oven cleaners. I dunno what you guys have in The States, but the cleaners i bought don't have "Lye" written on the cans, just the levels of sodium hydroxide and other main ingredients. To answer your question, 'regular' Easy Off Heavy Duty Oven Cleaner has plenty of sodium hyrdoxide/lye in it. The main active ingredients on the can I have here are listed as sodium hydroxide (54g/kg) and diethylene glycol alkyl eyther (55g/kg).

    I tried a couple of other oven cleaners, but had best results using the Easy Off Heavy Duty. Ray dobbins ('expert' bike restorer) suggests leaving it only for only 5 mins, but I found that quite a bit longer was necessary to remove the coating off the newer Shimano stuff -- perhaps he's only talking about the older Euro parts.

    If bits of the cranks have the coating worn off, try not to leave it on those parts for too long, and if there are scratches in the alu, make sure all the cleaner is removed from them when you've finished -- I think I left some cleaner in some scratches for quite a while, and it seemed to sink deeper!

    As others have said, when the oven cleaner has done/is doing its job, the cranks look a horrible grey/black mess, but they should buff up very well.

    I'm sorry to say, but I can't remember exactly how long I left the cleaner on for -- I think 15 to 20 mins. Either way, start conservatively, then increase the time as you get more 'courageous'

    Be aware that you'll lose the Dura-Ace logos.

    I then lightly hoesd off the excess cleaner; gave it a good, hard wipe and dry; then cleaned off most of the dark gunk with Brasso and a rag; then buffed with Brasso on a buffing pad drill attachement; buffed with Meguiar's Metal Polish, then hand polished with the Metal polish. I dunno if i had to buff with both the brasso and the Metal Polish, but it came out pretty good.

    As opposed to Ray Dobbins' tips, I recommend not using any steel wool, even the super fine stuff. I found that any steel wool scrathes the alu. Maybe he uses it lightly, which is probably just like rubbing hard with a rag. Also, he probably has better buffing equipment to get fine scratches out
    Last edited by 531Aussie; 05-04-10 at 01:25 AM.

  19. #19
    Biking Viking. goatalope's Avatar
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    Thanks for the detailed explanation. I'll give it whirl soon.
    Tuesdays I work on my hair helmet.

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