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Grit blasting for slippery plastic


Feb 29, 2004

 


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#250 Feb 29, 2004

Richard's advice is the best answer to this problem. Grit blasting

adds texture to the Delrin so your regular paint will adhere better.

Other Delrin/Celcon parts such as sill steps and air hoses need this

treatment too. Once done, the black plastic becomes a dull dark gray,

which, for trucks, is ideal as-is for some cars such as tank cars.



At the moment I do the grit blasting outside when the weather's decent

because I don't have a booth, and I use a CO2 tank as gas source, which

is not ideal for this (you use a fair amount of the gas), but I don't

do that much grit blasting, and it's portable and quiet. I have a

Paasche Air Eraser. Don't do it inside unless you have a booth,

otherwise the fine grit seems to get everywhere. Also, use a dust

mask; the kind with the little valves on them cost more but work much

better so that your glasses don't fog every time you exhale.



For Delrin you want to use aluminum oxide. I recently bought some 800

grit from Stone Age Products that works great; much less clogging than

the grit that came with the Paasche. Some recommend baking soda, but I

fing it takes several human lifetimes to get anywhere unless you are

working on extrmely small areas (to, say, remove lettering).



If you get an Air Eraser or the like you'll find it *very* useful, I

promise, and you avoid the hassle of blending or stocking yet another

kind of paint.



David Soderblom

Baltimore MD



On Sunday, Feb 29, 2004, at 04:32 US/Eastern,

weathering@yahoogroups.com wrote:

>

> Message: 9

> Date: Sat, 28 Feb 2004 17:59:42 -0800

> From: Richard Hendrickson rhendrickson@...>

> Subject: Re: Painting Slippery Plastics

>

>> Greetings:

>>

>> I posted this question on another list but upon further reflection,

>> you folks might have more experience with the issue.

>>

>> What type of paint would you recommend to paint plastics made with

>> Delrin or other slippery engineering plastics? I have several

>> freight car trucks made from this stuff I need to paint.

>>

>> Thanks in advance for your replies,

>>

>> John Gibson

>> Rocklin, CA

>

> John, I don't know of any paint that can be counted on to adhere to

> slippery engineering plastics like Delrin. However, I find that most

> paints will adhere well to truck frames and other Delrin parts if the

> parts are sandblasted first (making sure, of course, that in the case

> of

> trucks you mask the bearing cones so you don't sandblast them). I

> have a

> Badger grit gun powered by a hefty garage air compressor (most of the

> little compressors designed for air brushes don't deliver enough

> volume/pressure) and a home-made sandblasting booth with a plexiglass

> front

> that keeps the grit from going all over the place. I consider it an

> essential tool, as it prepares any surface for painting - brass,

> die-cast

> metal, resin, styrene - and also effectively removes unwanted paint,

> weathering, etc. And no, it doesn't damage fine detail on styrene or

> other

> plastic moldings if you use fine abrasive powder and apply it

> judiciously.

>

> Richard H. Hendrickson

> Ashland, Oregon 97520

>

>

David Soderblom

Operations and Data Management Division

Space Telescope Science Institute



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