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Removing paint form tub! Any ideas?
daniel mason - 7/12/14 at 10:26 AM

Paint/ bodywork are not my strong point and my new car needs tidying up a bit. The car is yellow but the tub is carbon fibre as is the front crash box. Is here any way to remove the yellow paint and exposing the carbon tub without damaging it?

snakebelly - 7/12/14 at 10:42 AM

Daniel,
I'm afraid the answer is just hard graft! Hopefully being a race car the paint will be pretty thin, fingers crossed!
Start off with something like a 240 or 320 grit paper wet and see how quickly you get through to the carbon. I wouldn't go much lower than a 240 myself but if its been applied with a trowel you may get away with 180. Once the majority is off then go to something like a 600 grit again wet until all the remaining paint is off then depending on how good a finish you want possibly go as far as 800 or 1200 wet. Coat of lacquer to seal and your good! sounds easy when you say it quickly!

I have know others use heat or chemical stripper on carbon but wouldn't even consider that myself, other may disagree...

HTH

Sam_68 - 7/12/14 at 11:11 AM

I can understand the caution, but I've used chemical stripper, even on polyester resin GRP, many times without adverse effects. Many people (including Miles Wilkins, I believe) use water soluble Nitromors without problems. The biggest issue is making sure that you've cleaned it all off completely before re-spraying, otherwise you will get a reaction with the new paint.

The epoxy resins generally used for carbon fibre are a lot more resistant to chemical attack than polyester, too.

Wet sanding of fibre composites isn't a brilliant idea, either, mind you - it's more likely that you'll abrade through the gelcoat into the structure of the fibres than using a stripper... Which makes it even more important to make sure that the composite is completely dried out afterwards (preferably using a low-bake oven), otherwise any moisture trapped in the fibres will inevitably make its presence felt as osmosis blisters, after the re-spray.

rdodger - 7/12/14 at 11:16 AM

Carbo lift!

http://eco-lifting.com/index.html

snakebelly - 7/12/14 at 11:34 AM

Sam, completely agree on the water issue should have made it clearer drying out is imperative, though in my experience if you take it slow and don't go too aggressively you can quite often see when your kissing the gel coat layer (presuming it has one!) before going through.

I would slightly disagree on the chemical not needing sanding after though as you'll need to key the surface for lacquer unless your just planning to strip and leave whatever is underneath as you find it, but if your not that bothered I would just key the paint and paint over in black gloss or the like.

If you have a low bake oven that's fine but I have used a hot air gun on low from about 18" just to warm the surface and encourage any remaining moisture. Lets not forget this is a race car, there not know for show quality paint! :-)



quote:
Originally posted by Sam_68
I can understand the caution, but I've used chemical stripper, even on polyester resin GRP, many times without adverse effects. Many people (including Miles Wilkins, I believe) use water soluble Nitromors without problems. The biggest issue is making sure that you've cleaned it all off completely before re-spraying, otherwise you will get a reaction with the new paint.

The epoxy resins generally used for carbon fibre are a lot more resistant to chemical attack than polyester, too.

Wet sanding of fibre composites isn't a brilliant idea, either, mind you - it's more likely that you'll abrade through the gelcoat into the structure of the fibres than using a stripper... Which makes it even more important to make sure that the composite is completely dried out afterwards (preferably using a low-bake oven), otherwise any moisture trapped in the fibres will inevitably make its presence felt as osmosis blisters, after the re-spray.

snakebelly - 7/12/14 at 11:38 AM

Hmm looks interesting but at US$ 195 for 4 litres plus shipping and duty im guessing its going to work out expensive!


quote:
Originally posted by rdodger
Carbo lift!

http://eco-lifting.com/index.html

Sam_68 - 7/12/14 at 11:53 AM

quote:
Originally posted by snakebelly
I would slightly disagree on the chemical not needing sanding after


No, I didn't say (or mean to imply) that chemical stripping will mean you need no sanding/flatting whatsoever - both to get rid of the last traces of paint, and to slightly abrade the surface to provide a key for the paint/lacquer, but it'll be a lot less aggressive than completely sanding the paint off (hence my saying you're more likely to abrade through to the fibres with complete abrasive stripping of the paint).

But if you get rid of most of the paint using a stripper, you can limit final sanding/flatting to 800 grit or finer, which causes much less damage to the gelcoat layer.


Each to their own, though - I can understand people not wanting to risk using stripper, but I'm far too lazy and have better things to do with my time than engage in endless house of sanding and flatting!

snakebelly - 7/12/14 at 01:09 PM

couldn't agree more Sam, which is why I would flat it back and paint it :-)

JC - 7/12/14 at 01:46 PM

Certainly on aircraft, only mechanical methods are permitted when removing paint from Carbon panels - lashings of elbow grease I'm afraid!

daniel mason - 7/12/14 at 06:41 PM

Thanks guys. How do you apply the chemical stripper?

Sam_68 - 7/12/14 at 06:53 PM

quote:
Originally posted by daniel mason
How do you apply the chemical stripper?


Basically just stipple it on with a brush - but remember you'll be rinsing it off, once you've finished, so you need to be somewhere you can swill water around. And well-ventilated is a good idea, too!

daniel mason - 7/12/14 at 08:09 PM

And it will only take of the top paint layer? And not damage the top coat of carbon?
It's a proper carbon autoclaved tub is the force and desperately don't want to damage it!

Sam_68 - 8/12/14 at 03:11 AM

It will take off as many layers of paint as there are!

If it's autoclaved carbon, it will be epoxy - which is pretty inert stuff - rather than polyester resin.

Personally, I've never had any issue even with polyester resin, but there are those who believe that if you leave the paint stripper on long enough, it will soften polyester resin

Obviously, you shouldn't leave the stripper on any longer than is necessary for it to do its job and if you're worried, try it on a small, unobtrusive area first.

As previously mentioned, the biggest issue is making sure that you have completely removed any stripper that has foinf its way into cracks or pores on the surface of the gelcoat, but again this should be a minimal problem on autoclaved carbon, since the sut=fface should be a lot more consistent and free from such defects than old-fashioned wet layup polyester GRP.

Andy S - 8/12/14 at 09:55 AM

I would have a chat with the manufacturer and see what experience they have - Soda blasting may be an option.