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I need help on the steps to spray paint plastic?

I want to repaint some plastic computer side panels silver, so I found some silver spray paint for plastic. 

But, Should I use plastic primer and if i use plastic primer do I still have to use the special plastic spray paint and Should i use a clear coat when I'm all done painting it.

Note: The panels do have some deep scratches 


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caarntedd5 years ago
Advice I once received from an old spray painter was if the object you are painting has no paint on it, you need to prime. If it already has paint on it that is in good condition, prepare the surface (sand etc.) and paint without priming. This is "backyard" advice, not a professional method, but it has always worked for me.

So yes, prime your surfaces.
master key (author)  caarntedd5 years ago
What grit sand paper should I sand plastic with.
Sorry for the late reply. I'm having some problems with my computer at the moment.

First things first. Before you actually do anything with the panels, always test your method on an inconspicuos spot such as the inside surface where it will not be seen. The texture on the inside of your panels may not be the same as the outside, but you will get an idea of the performance of the products you wish to use.

If you have deep scratches you will need to use a coarse grit paper in a circular motion over the scratched area. Sanding by hand, not with an electric sander ,will give better control and a better finish on what is essentially a small area of a soft material. Try 80 to100 grit which is not really that coarse if you were sanding something other than plastic, but should be OK.
A bit of trial and error on an inconspicuos spot will help with selection of materials. Then move to a finer grade such as 150 or 180, and move in a circular motion to remove the scratches you have made with the coarse paper, moving outwards over a larger area to blend the sanded area into the unsanded area without creating an obvious dent. If the panels have a textured surface you will need to sand all over them at this stage to make the surface look even.

Move to a finer grit if you think the surface is not smooth enough and continue sanding, remembering that any defects left in the early preparation stages will be compounded with each layer of primer/paint and give a bad finish at the end.

Once the sanding stage is complete wipe the surface with something like methylated spirit on a rag to remove dust and oil. It will dry quickly and is not very harsh on plastics. Some other solvents and paint thinners will destroy your panels. Then you will be ready to prime.

Two thin coats of primer, allow to dry, and then you are ready for colour. Wipe with the spirit again and apply your paint. A light sand wih very fine sand paper, 300 to 600 grit between coats (after they are dry), not really required, but will improve the finish. Keep painting until you are happy with the result.

This is a very rough tutorial (that can be adapted to anything) on surface prep and painting, but it will give you an idea of where to start. You may need more preparation than this, or you may need less.
A few rules to stick by:
As Burf says, always read the manufacturer's instructions.
Take your time and don't take shortcuts.
Use a sanding block, especially when sanding flat surfaces.Your bare fingers will create low spots.
The higher the number on your sandpaper, the finer the finish it will give.
In general the types of sandpaper that are suitable for metal surfaces are good for plastic (this is not a strict rule, so try whatever you have at hand. Practice and good technique will get you through).
Always try your method on a spot that won't be seen if you are not confident.

These tips are just a rough guideline, not a professional method. You should experiment yourself (as I and many others do every day) and you too will become a "backyard "expert.

It sounds to me like a lot of trouble for a computer, but if you are determined to do this, you should also consider using a spray on putty or filler to fill the scratches between the initial rough sanding and the smoother stages (then prime) to gve a nice even finish. Personally, I would give the panels a quick sand with 100 to 150 grit, wipe with methylated spirit, one coat of primer, 2 or 3 coats of paint.

Sorry for the length of this answer, but this is something that can't really be taught this way, you need to try it yourself. Good luck, hope this helps a little.



master key (author)  caarntedd5 years ago
Will it give a smooth surface?
No. Preparation gives a smooth surface finish.
Burf5 years ago
Read the instructions on the paint can label. Some paints for plastic require primer or a base coat, some don't. The paint maker is the authority.
Repair the scratches prior to primer or paint. I have found that JB Kwik weld works well as a filler/putty on most plastic