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Black aluminum ----> Raw aluminum?

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Black aluminum ----> Raw aluminum?

Old 05-04-09, 07:04 PM
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hypnotoad
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Black aluminum ----> Raw aluminum?

So I recently bought a new Raleigh Clubman and I can't help thinking how much better it would look if the stem, handlebars, and seat post were raw aluminum instead of black. Looking at the scuff marks where i've adjusted the seat post it appears that underneath the black is a nice silvery raw aluminum color that i feel would go way better with the overall color scheme of the bike ("graphite" and silver). This led me to beleive that disassembling these components and stripping the paint could accomplish what I'm after. Am I right or is it somehow more complicated? What would be the best way to get rid of the paint? Could I just soak them in thinner or is there some horrible consequence I'm not thinking of?

Anyway, sorry if this is a stupid question. I tried a few searches but didn't find what i was looking for.
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Old 05-04-09, 07:40 PM
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It can be done. Bear in mind the black coating is not actually paint, it's an anodized finish. There are various methods to use to remove anodizing. Some involve oven cleaner and whatnot. But I've found that simply spending some time polishing with some very fine grade steel wool worked as well as anything. I polished a black Ritchey stem in this manner. Be aware that after you remove the black anodizing, that the aluminum will be "raw" and will tend to dull over time and occasionally need polishing to restore the shine.
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Old 05-05-09, 07:37 AM
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Easy Off oven cleaner will remove anodizing very quickly. You may hve to apply it nore than once, rinsing in water between applications. When the metal turns a uniform dark gray, the anodizing is gone. Don't leave it on too long or it will begin to eat the aluminum. Go over it with 0000 steel wool and then start polishing. I use a cotton wheel and tripoli compound, but metal polish and a lot of rubbing will get it done.

Some black parts are painted, in which case the oven cleaner will have no effect. Use paint stripper on those.
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Old 05-05-09, 07:55 AM
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Originally Posted by Dirtdrop View Post
Easy Off oven cleaner will remove anodizing very quickly. You may hve to apply it nore than once, rinsing in water between applications. When the metal turns a uniform dark gray, the anodizing is gone. Don't leave it on too long or it will begin to eat the aluminum. Go over it with 0000 steel wool and then start polishing. I use a cotton wheel and tripoli compound, but metal polish and a lot of rubbing will get it done.

Some black parts are painted, in which case the oven cleaner will have no effect. Use paint stripper on those.
I would caution using alkali products such as Easy-off on aluminum. Yes it will remove the surface anodization but alkali also reacts with the aluminum. You have no control of the amount of reaction in the underlying, unoxidized aluminum. You will also have no idea of the damage you may cause. The alkali will tend to follow the crystallite boundaries in the part and may cause weaknesses that can lead to eventual breakage of the part that you are treating.
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Old 05-05-09, 11:48 AM
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Anodized

My experience with aluminum bars is that even the silver ones are actually silver anodized not raw aluminum. Raw aluminum tends to oxidize and get dull. So you may want to do some spot test first. You can surely polish the raw aluminum. I'm not sure how correct thtis is but my experience only.
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Old 05-05-09, 11:54 AM
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Originally Posted by cyccommute View Post
I would caution using alkali products such as Easy-off on aluminum. Yes it will remove the surface anodization but alkali also reacts with the aluminum. You have no control of the amount of reaction in the underlying, unoxidized aluminum. You will also have no idea of the damage you may cause. The alkali will tend to follow the crystallite boundaries in the part and may cause weaknesses that can lead to eventual breakage of the part that you are treating.
You're overthinking it . Easy Off is lye, and it water neutralizes. Wash and buff and you're fine.
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Old 05-05-09, 11:58 AM
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I don't think alkali products are a good idea as you don't really know how much you will eat the aluminum. If you do want to use some, don't leave it on for very long, and be sure to wash it off.
Also, it could be anodizing, or a powder coat. If you can't tell which I can't help you over the internet. That said, either way you should be able to sand it off, although it will take a while. The observation about silver aluminum being usually anodized is also correct. Aluminum takes a rather ugly surface finish unless you polish it regularly, or clear coat over it. Note, many factory car rims which are aluminum do in fact have a clear coat, even if it is difficult to detect. If you have a polishing wheel, that may make the surface oxidation uniform enough that it will hold a uniform shine for a while, but you'll still have to repeat the polish every now and then.
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Old 05-05-09, 02:01 PM
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The NaOH reacts MUCH, MUCH more strongly to the aluminium-oxide anodizing. The initial reduction takes place quickly and the bare aluminium is taken off much slower. Besides, the rate-limiting step is how much base you have on the surface. Apply just a little, just sufficient to react with the anodizing, and that's all that's used in the reaction. In most cases, you have to re-apply more because the initial amount was insufficient. Very little is left to react with the aluminium and even then, that reaction is much, much slower anyway.

Follow up with some Mother's or BlueMagic metal-polish and you've got a nice shiny surface.

Those who shy away from this procedure have obviously not done it.
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Old 05-05-09, 02:42 PM
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I have a lot of experience with the process. Just about everything on this bike is stripped and polished.


This crank was beat up when got it, so I had to strip the anodizing and sand out the scratches and gouges.



This is what happened when I fell asleep and the post soaked for hours instead of seconds. It was a cheap post, anyway.



You could also have the parts chromed.



I had this stripped and polished an hour after the mailman delivered it. It had scratches that I couldn't live with.


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Old 05-05-09, 04:32 PM
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Originally Posted by CCrew View Post
You're overthinking it . Easy Off is lye, and it water neutralizes. Wash and buff and you're fine.
Not over thinking it. Lye is the common name for sodium hydroxide (NaOH). Sodium hydroxide reacts with aluminum to form aluminum hydroxide and hydrogen. It will fizz. While the anodized layer is relatively inert, it will dissolve in the NaOH and is a relatively porous layer because of the way the part is anodized. And since the point is to remove the anodization, the bare aluminum metal is exposed to the NaOH and is not inert to the NaOH at all.

NaOH isn't neutralized by water either. It is dissolved by water and can be rinsed away but it is still a basic substance that is available to do all the things that bases do. Acids will neutralize a base and make it something else...a salt...however water only causes a physical change.
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Old 05-05-09, 04:51 PM
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Originally Posted by DannoXYZ View Post
The NaOH reacts MUCH, MUCH more strongly to the aluminium-oxide anodizing. The initial reduction takes place quickly and the bare aluminium is taken off much slower. Besides, the rate-limiting step is how much base you have on the surface. Apply just a little, just sufficient to react with the anodizing, and that's all that's used in the reaction. In most cases, you have to re-apply more because the initial amount was insufficient. Very little is left to react with the aluminium and even then, that reaction is much, much slower anyway.

Follow up with some Mother's or BlueMagic metal-polish and you've got a nice shiny surface.

Those who shy away from this procedure have obviously not done it.
Other way around. The oxide...which is what the anodization process puts in place...is a relatively inert material. It's a ceramic that forms naturally on bare aluminum (about 4 nm thick) when the aluminum is exposed to air. By attaching it to an anode in an acidic bath, you can form a much thicker layer. The oxide layer will resist the alkali for a while until alkali has worked through to the underlying metal. Once in contact with the bare metal the reaction is very rapid. It effervesces rather vigorously.
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Old 05-05-09, 04:52 PM
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The idea is not to soak it in a tub of lye. Rather spray on just enough Easy-Off so that it'll react with just the surface layer anodizing. Typically it's not enough and you'll need to spray a 2nd layer. There won't be enough remaining to harm the aluminium.

Just because some people have pinched tubes and blowouts when mounting a tyre, doesn't mean that everyone who does it will experience the same failures. In fact, the numbers of people who've had bad experience with Easy-Off is overwhelmingly outnumbered by those who've used it correctly and gotten good results.
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Old 05-05-09, 05:17 PM
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Originally Posted by cyccommute View Post
Other way around. The oxide...which is what the anodization process puts in place...is a relatively inert material. It's a ceramic that forms naturally on bare aluminum (about 4 nm thick) when the aluminum is exposed to air. By attaching it to an anode in an acidic bath, you can form a much thicker layer. The oxide layer will resist the alkali for a while until alkali has worked through to the underlying metal. Once in contact with the bare metal the reaction is very rapid. It effervesces rather vigorously.
If that was really the case, we would have a pristine molted layer of anodizing. Like a crab shedding its skin. After soaking a seatpost in lye, we'd have zero seatpost left with a perfect shell of anodizing left in the original color. However, no such pristine casing exists after using Easy-off on anodzing.


You might want to review your oxidation/reduction chemistry:

1. Anodizing aluminium is endothermic oxidation process requiring the addition of energy. Typically 20-amps per square-foot. There are actually two reactions going on:
a) An electrochemical reaction, is the oxidation of aluminum to form the aluminum oxide

b) A chemical reaction, taking place at the surface of that oxide layer and which consists of the chemical attack of the oxide film by the acid. This forms the hexagonal lattice.
2. The opposite reduction using a base is exothermic and produces heat. While the aluminum oxide is inert to most materials, it's strongly attacked by a base. Which does the opposite reaction and removes oxygen from the anodizing.


The idea isn't qualitive yes or no, all or nothing, black & white. It's a quantitative technique of picking the right amount of Easy-Off to just remove the anodizing.
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Old 05-05-09, 05:40 PM
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Glass beads!! Then super fine sandpaper such as 1000-1500, and hand polish to a high chrome like shine. Might cost a little to get blasted, but it will leave a soft satin finish that will polish out fine.,,,,BD
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Old 05-05-09, 05:41 PM
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Originally Posted by DannoXYZ View Post
If that was really the case, we would have a pristine molted layer of anodizing. Like a crab shedding its skin. After soaking a seatpost in lye, we'd have zero seatpost left with a perfect shell of anodizing left in the original color. However, no such pristine casing exists after using Easy-off on anodzing.
I said that the oxidized layer will resist the reaction with the alkali for a while. I did not stay that it would resist it completely. The reaction between aluminum and the alkali is very rapid while the reaction between the alkali and the oxide layer is much slower.

Originally Posted by DannoXYZ View Post
You might want to review your oxidation/reduction chemistry:

1. Anodizing aluminium is endothermic oxidation process requiring the addition of energy. Typically 20-amps per square-foot. There are actually two reactions going on:
a) An electrochemical reaction, is the oxidation of aluminum to form the aluminum oxide

b) A chemical reaction, taking place at the surface of that oxide layer and which consists of the chemical attack of the oxide film by the acid. This forms the hexagonal lattice.
So far so good and pretty much what I said above.

Originally Posted by DannoXYZ View Post
2. The opposite reduction using a base is exothermic and produces heat. While the aluminum oxide is inert to most materials, it's strongly attacked by a base. Which does the opposite reaction and removes oxygen from the anodizing.
I believe that you are wrong in stating that this reaction is exothermic. The Bayer process requires heat to dissolve the aluminum oxide in bauxite with sodium hydroxide. That does not imply an exothermic reaction.
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Old 05-05-09, 06:12 PM
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Old 05-05-09, 06:28 PM
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Once again, skip the chemicals, and get them bead blasted.,,,,BD


This sounds like the oil discussions on the automotive boards
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Old 05-05-09, 06:30 PM
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OP, as you can see this is why I suggested going at it with some fine steel wool for a few hours.
Start with about 000 grade and then go to 0000 grade.
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Old 05-05-09, 07:05 PM
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I certainly agree that the Clubman would look better with chrome or silver bars, stem, and seatpost... but you do know that those can be purchased at bike shops, don't you? Also, since the bike is presumably out-of-the-box stock, taking some care to choose a different length or rise stem, a different width or shape handlebar, or a different set-back seatpost (as well as silver in colour) can make the bike fit better as well as look better.

I suggest new bars rather than polishing because I once worked with a guy who sanded his aluminum mtb bars to make them shiny and wound up with an imprint of his stem in his lip and a few broken teeth.

Congrats on the sweet bike, though... I was very impressed when I saw it on their interweb pages.
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Old 05-05-09, 07:55 PM
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Originally Posted by hypnotoad View Post
So I recently bought a new Raleigh Clubman and I can't help thinking how much better it would look if the stem, handlebars, and seat post were raw aluminum instead of black. Looking at the scuff marks where i've adjusted the seat post it appears that underneath the black is a nice silvery raw aluminum color that i feel would go way better with the overall color scheme of the bike ("graphite" and silver). This led me to beleive that disassembling these components and stripping the paint could accomplish what I'm after. Am I right or is it somehow more complicated? What would be the best way to get rid of the paint? Could I just soak them in thinner or is there some horrible consequence I'm not thinking of?

Anyway, sorry if this is a stupid question. I tried a few searches but didn't find what i was looking for.
DON'T DO IT!

Everytime I've tried something like this, no matter how good my intentions were, it has never worked out to be worth it or up to my expectations...

Why not get aluminum parts with a clear anodizing?
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Old 05-05-09, 08:19 PM
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How about just swapping the parts for ones with the finish you want? Sounds like WAY less trouble to me.
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