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Old 02-23-06, 07:18 PM   #1
LoveParkRIP
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Is it possible to sandblast a frame, and apply clear coat only?

I'd like to get my bike repainted, but I just want the bare metal to show through. I figure I could have a friend sandblast the old paint off, and then I could have a clear coat applied. Would this work?

-Chris
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Old 02-23-06, 07:30 PM   #2
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yea. I had a frame I built blasted and then powdercoated clear. it turned out really nice. looks metal-flake-ish. with a little of the HAZ showing. here's a pic:
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Old 02-23-06, 09:49 PM   #3
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That's a good look. Did they actually blast it with sand, or use a gentler media.
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Old 02-24-06, 12:45 AM   #4
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I remember seeing a DOGS BOLX released in clear powdercoat as well. There's no reason why not. It's just see-through paint, after all.
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Old 02-24-06, 01:29 AM   #5
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Quote:
Originally Posted by LoveParkRIP
I'd like to get my bike repainted, but I just want the bare metal to show through. I figure I could have a friend sandblast the old paint off, and then I could have a clear coat applied. Would this work?

-Chris


I think the reason that a "clear coat only" is isn't done commonly is because clear coat without primer + paint is actually quite porous compared to "clear coat + primer + paint". I know a person that did clear coat only without the primer + paint and still got lots of rust under the clear coat after only a few months.

We need an actual paint expert in here to comment on this because I'm not sure. Is there a paint doctor in the house?! If there was some way to do it so that rust isn't that much of an issue, well that would be great. Unfortunately, I think that you are going to get rust under the clear coat without any primer & paint underneath.
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Old 02-24-06, 02:47 PM   #6
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Originally Posted by Peterpan1
That's a good look. Did they actually blast it with sand, or use a gentler media.
I'm not sure what media they used. the place was a bit caveman so it may have been sand.
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Old 02-24-06, 06:02 PM   #7
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Quote:
Originally Posted by bellweatherman
I think the reason that a "clear coat only" is isn't done commonly is because clear coat without primer + paint is actually quite porous compared to "clear coat + primer + paint". I know a person that did clear coat only without the primer + paint and still got lots of rust under the clear coat after only a few months.

We need an actual paint expert in here to comment on this because I'm not sure. Is there a paint doctor in the house?! If there was some way to do it so that rust isn't that much of an issue, well that would be great. Unfortunately, I think that you are going to get rust under the clear coat without any primer & paint underneath.
A clear coat, from the point of view of water uptake is the same as paint, but you're right about the primer making a substantial difference. However, that's only really because of the overall thickness layer. All paints are porous, to a lesser or greater extent, as there is no such thing as a waterproof polymer. Go look at that orange tupperware you cooked beans in once and was never more colourless. When you've got the three stage coat, you've got substantially more material down on the substrate than if you pop a few coats of baked-on lacquer on. A primer and base coat is no more dense than a lacquer, in fact, less so, because the lacquer is almost pure hard binder, rather than a dispersion of particles in a binder that don't fully wet at their interfaces.

How many coats of clear do people who clear-coat put on by comparison to the depth of three-stage? I'll wager it isn't as many.

And you have to remember, until you get the hydrated expansion of rust, you have no idea what's going on under your opaque paintjob....
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Old 02-24-06, 09:17 PM   #8
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i would suggest a powder coat, you can get a variety of clear coats, some with metal flakes for a shimmer, matte or glossy. powder coats, though not as nice looking as a nice paint job can be are super strong and will not chip.
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Old 02-26-06, 09:13 AM   #9
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Quote:
Originally Posted by Falanx
A clear coat, from the point of view of water uptake is the same as paint, but you're right about the primer making a substantial difference. However, that's only really because of the overall thickness layer. All paints are porous, to a lesser or greater extent, as there is no such thing as a waterproof polymer. Go look at that orange tupperware you cooked beans in once and was never more colourless. When you've got the three stage coat, you've got substantially more material down on the substrate than if you pop a few coats of baked-on lacquer on. A primer and base coat is no more dense than a lacquer, in fact, less so, because the lacquer is almost pure hard binder, rather than a dispersion of particles in a binder that don't fully wet at their interfaces.

How many coats of clear do people who clear-coat put on by comparison to the depth of three-stage? I'll wager it isn't as many.

And you have to remember, until you get the hydrated expansion of rust, you have no idea what's going on under your opaque paintjob....

Primer coats are designed to bond to metal and provide a barrier surface for the top coat to bond to. Clear coats do not have the same characterists. One possible exception is clear powder paint and/or the clear used to protect aluminum parts - such as automotive wheels.
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Old 02-27-06, 12:31 PM   #10
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Originally Posted by LoveParkRIP
I'd like to get my bike repainted, but I just want the bare metal to show through. I figure I could have a friend sandblast the old paint off, and then I could have a clear coat applied. Would this work?

-Chris
POWDERCOAT over bare metal works GREAT! You can sand (60 mesh)blast it first as pictured above. Or you can use a ScotchBrite pad (course for steel) and give it a grainy look. Be sure to get it to the PCer ASAP!! bare metal rusts QUICK! Mask seat tube, etc!
Powdercoat comes in lots of kind of "clear", Candy red,blue,green, purple, etc. Clear w/pearl etc. A good PCer can even whip up something of both, would bet.

FOR FULL PROTECTION; Spray a quality clear PAINT over the powdercoat. Clean it WELL with wax & grease remover before spraying the clear though. Certain kinds of decals (some "sticker" types) should go on last. thin DECALS (not stickers or cut vinyl) can be applied over the powdercoat and UNDER the clear PAINT.

My $.02,
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Old 02-28-06, 01:47 PM   #11
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Quote:
Originally Posted by Nessism
Primer coats are designed to bond to metal and provide a barrier surface for the top coat to bond to. Clear coats do not have the same characterists. One possible exception is clear powder paint and/or the clear used to protect aluminum parts - such as automotive wheels.

The primer is there to provide a smooth, dense coat so that the paint doesn't need forteen layers for good covering and opacity. Certain types of primer provide a degree of cathodic protection, but not many. They're all much denser (in terms of mass, not porosity) than the paint because of the filler component, but none of this equates to any better barrier protection. multiple fine layers of paint provides lots of fresh interface that requires broaching again and again. A thick layer of primer may be no more protection than lots of fine layers of paint if well-bonded, perhaps less. The counter-argument is that the paint-only option may be more prone to chipping. Primers don't tend to set hard, but they are tough.

And you're right. If you're going to do it, powder coat is the way
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Old 02-28-06, 01:56 PM   #12
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The trick to this is to wax the hell out of the clear when you're done in order to minimize porisity and moisture intrusion.

Clears tend to 'leak' a bit.
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