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Old 05-15-09, 09:12 AM   #1
Banzai
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Stripping powdercoat

Anything the home mechanic can do?

I had a frame done by a powdercoater...he put the stuff on so thick that I can't even clamp a front derailler to it. He also says he won't pay to strip it to re-do it since I didn't specify things like coat thickness, etc.

I can't sandblast it...it's aluminum.

There's no one around here that does media blasting.

Thoughts?
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Old 05-15-09, 10:31 AM   #2
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Instead of stripping it and starting over at considerable time/expense, how about sanding the paint precisely where you need to clamp?
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Old 05-15-09, 01:32 PM   #3
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Instead of stripping it and starting over at considerable time/expense, how about sanding the paint precisely where you need to clamp?
this.

get some wet-or-dry 220grit sandpaper. preferably silicon carbide over aluminum oxide because it's harder, but Aluminum oxide sand paper will work too, it's just slower because it's softer.
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Old 05-15-09, 02:55 PM   #4
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Don't sand your new paint job. Get a Dremel tool and a little sander attachement and "adjust" the derailler clamp diameter a little larger and it will fit the thicker paint. Sand a little then check, repeat until it just barely fits the tube
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Old 05-15-09, 03:09 PM   #5
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Nope. I want to get rid of it. It's frakking thick...it makes the whole frame look kind of, I don't know...soft and gooey, I guess.

The guy who did the coating apparently has no capability to strip the coating...he says he won't pay for it to be done, either. He's offered to re-do the job for free if I pay to have it stripped, but I won't do that because I don't want a repeat.
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Old 05-15-09, 03:20 PM   #6
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There are specialized strippers which will remove epoxy or vinylester powder coats, but I've only seen them available in commercial quantities. They are expensive and very toxic.
IMO, your best and safest option is to pack the frame up and send it to a media blaster elsewhere. In Oz, the cost of stripping a powder coated bike frame would be around $US50.
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Old 05-16-09, 05:33 AM   #7
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If you want to get rid of the paint then, your only option is to send it to someone who can do the whole job properly. It's tough to swallow, but a suggestion is to eat the cost of what was done, and seek someone else. Do you really trust this person can do it right the second time? He's obviously not done a frame before. Save yourself further headache, send it so someone who will media blast it, and paint it right. No worries. There's gotta be good ones in Austin or San Antonio.

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Old 05-16-09, 09:14 AM   #8
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http://www.pfonline.com/articles/cli...00cl_pwd1.html

Reading the above, you can't use a typical caustic hot tank to strip the paint because it will eat the aluminum. Media blasting would have to be done expertly also, or frame damage might occur.

I would measure the ST diameter to get an idea of how thick the coating really is. A braze-on adapter or a clamp on FD could be honed out to a slightly larger ID, but that might not be real cheap to get done either. An adjustable height braze-on adpater could be left on the frame as semi-permanent.

If you try sanding the ST to reduce the diameter, I would not use 220 grit for very long. Use 400 for most of the work and switch to 600 near the end of the job. After that, the coating should be able to be buffed out to a sheen that is close to the rest. If coarser grits are used, you would want to apply masking tape and restrict the sanding to just the clamp area and no more.

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Old 05-16-09, 05:35 PM   #9
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I just got my frame powder coated (badly - too thin). I needed to strip a bit off on critical areas and there were two things that worked very well.

The first one (deliberately used) was an automotive product whose category is "gasket remover." Sprayed that stuff on, let it sit for a few minutes, wiped off most of the powder coat. If you are trying to only remove specific parts of your powder coat, you MUST MASK CAREFULLY, before spraying the gasket remover.

The second product (accidentally discovered - not in a good way) was when I decided to paint over my powdercoat. I took some acetone to the powdercoat to remove any grease on the frame.......well the acetone started to dissolve the powdercoat immediately! With a putty knife and a rag soaked in acetone, you could take off powder coat where ever you wanted.

Hope this helps,
Leslie
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Old 05-16-09, 06:06 PM   #10
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another thing you might want to do for kicks is lightly sand an area with 600 grit wet/dry sandpaper and see how it looks. if it loses its luster (and you like luster), you can try wiping a little Pledge on it. this might allow you to take away the "gooey" appearance and save you the hassle of getting a job paint/powdercoat job.
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Old 05-16-09, 10:57 PM   #11
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Paint stripper will remove powdercoat.
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Old 05-17-09, 11:25 AM   #12
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I just got my frame powder coated (badly - too thin). I needed to strip a bit off on critical areas and there were two things that worked very well.

The first one (deliberately used) was an automotive product whose category is "gasket remover." Sprayed that stuff on, let it sit for a few minutes, wiped off most of the powder coat. If you are trying to only remove specific parts of your powder coat, you MUST MASK CAREFULLY, before spraying the gasket remover.

The second product (accidentally discovered - not in a good way) was when I decided to paint over my powdercoat. I took some acetone to the powdercoat to remove any grease on the frame.......well the acetone started to dissolve the powdercoat immediately! With a putty knife and a rag soaked in acetone, you could take off powder coat where ever you wanted.

Hope this helps,
Leslie
That does help...thanks for the tip.

How "clean" was the frame after the chemicals did the work? I.e. would it be suitable for re-paint?
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Old 05-17-09, 08:36 PM   #13
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That does help...thanks for the tip.

How "clean" was the frame after the chemicals did the work? I.e. would it be suitable for re-paint?

I didn't actually try to clean my entire frame, so I can't give you a precise answer. I was just trying to clean the powdercoat off the brake bosses (which the powder coater was told to mask, but didn't). I then just painted over the poorly done powdercoat with tremclad rust paint, to build up the areas that were too thin.

Now, to actually try to answer your question (apologies due to extreme fatigue right now)
The chemicals I used seemed to "soften up" the powdercoat. It seemed to become sticky and soft, so that it was easily scraped off. Kind of like a slightly sticky molasses. I could mostly wipe the powdercoat "goo" off with a rag, or use a putty knife and scrape it off.
I think if you wanted to totally strip a frame using this method, the chemicals would take 95% of the powdercoat off. It seemed like it would be difficult to get the gooey powdercoat remains out of the crevices between the tubes of the frame. Perhaps at this point a light sandblast would remove the rest? I'm not sure.

However, given that I just wanted to thin out my powdercoat in a few spots this method (spray on chemicals - wipe/scrape off) worked well. I just cleaned the whole thing up with a few coats of rust paint afterwards. It was only a pain because it should have been done right by the powdercoaters and it took me a week or so to get the paint on and dry.

Hope this helps
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Old 05-17-09, 09:10 PM   #14
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I believe that bare aluminum frames are prepped for paint with walnut shell or soda blasting. I know that glass bead blasting is used for steel, but is too abrasive for aluminum.
I've also heard that a cold soak tank full of acetone will strip powder coat from a frame. Got to be careful though, because it's extremely flammable.
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Old 05-17-09, 09:26 PM   #15
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I've also heard that a cold soak tank full of acetone will strip powder coat from a frame. Got to be careful though, because it's extremely flammable.


Acetone will indeed strip it. I found that out by accident.

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