Help with prep techniques

K

KingQuarter

Guest
Sooo i took on a big project it's a motorcycle for a buddy. The gas tank is metal and the ferrings are plastic.

Question 1,
One of the ferrings is cracked how can I repair it?

Question 2,
How do I prep the plastic to paint it
And how do I prep the metal tank to paint.
(Both have paint on them, the metal tank has a clear coat and the ferrings have no clear coat just paint)


Thanks very much for any help.


Just a noob in a world of pro's.
 
The tank, if the paint is in good shape just clean good, scuff or sand to remove all gloss, clean again and tack rag. Then a sealer should be applied and then paint and clear.

The fairings should also be given a similar treatment, just make sure they are painted, and not molded in color. Plastics generally need a plastic primer and and adhesion promoter, also a flexible primer sealer for plastics is recommended. Then you can go through the normal routine. As for the plastic repair, go to a good auto parts store, one that also sell paint supplies, and ask them what they have to do the repair. Probably a 3M product of some kind. The crack will have to be ground out a bit, so the repair material can go in and bond it all together, also a patch material and more plastic bonder should be used behind the crack for better strength.


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Question 1- Needs to be plastic welded, their are guys around that specialize in plastic welding, you can try a home fix, fit a metal panel to it on the inside with short screws and fill with epoxy resin, then take the screws out once the resin is cured and epoxy the top crack and screw holes, sand and base coat it..I'd suggest the plastic welding though done by a pro if your unsure..

Question 2- Few ways really, depends on the condition of the paint, if your changing the base coat color etc but generally i'll sand the previous paint well with about 400 grit wet and dry or completely back to metal if needed (pending on its condition or actually what its been painted with prior)..Chuck another base coat on or if taken back to metal use a primer then base coat, then hit the base with about 800 grit wet and dry and then with 1000 grit wet and dry, once hit with a thousand grit its ready to airbrush after degreasing it..Airbrush and then clear...The plastic can be prepped in a similar fashion, is the plastic actually painted or has it been molded in that color? Generally get a nice bite to it with again about 400 grit, heres the difference, you may need to put on an adhesion promotor or buy a different type of auto paint specifically designed for plastic chemical bonding, sand that layer back with a similar grit as to metals and then base, sand again to 1000 grit and then airbrush and clear..

Thats the basic way I generally go about it..others may have different suggestions as really there are a few ways of going about it, the above method I use is mainly due to the fact I learnt that airbrushing straight onto a plastic surface can be a cow and the paint has a habit of peeling off easily unless prepped properly..GL
 
The ferrings are not molded. Just spray painted. And should I clear coat then airbrush over the clear then clear again? So if I miss up airbrush I won't mess up my automotive pearlescent. And what grit for the metal tank?


Just a noob in a world of pro's.
 
^ Clearing the base first is fine if you feel you may make a booboo, personally I don't do that as what your kinda doing is setting yourself up for failure by putting some doubt in your mind LOL..In the long run it is safer but an artwork can be lightly sanded or washed off with a good rub of degreaser, especially in the earlier planning layers where mistakes may happen..I just make sure the base is well cured prior to starting to airbrush it or even bake it in the sun for a good few hours and even a light clean with thinners won't bother it..you can also use a mid clear rather than a full clear..Do you want to take the tank back to metal or just prep the paint thats on it? Pre-existing paint and clear I hit with 400 grit to mainly remove the clear, then I'll use about an 800 to lightly prep the actual base color, then with 1000 or 1200 grit to airbrush prep that base, if your going back to metal and redoing it all then it kind of depends on how good or bad you can lay the flat coat LOL but its pretty much a similar process..From metal go with your primer, rub that with 400 especially if you use a high build..Spray on your base, rub that with 800 to flatten any orange peel. Just prior to fully flattening the orange peel I'd use 1000 or 1200 for final airbrush prep..When using the wet and dry make sure to add a bit of dishwashing detergent or soap to the bucket, use a water hose to have a constant water flow onto the paper and keep checking to make sure any paint isnt accumulating in the paper that may cause scratches..GL
 
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