So i found someone locally who paints, he asked me to prep my sideskirt before I bring it in for paint.

Do I just scuff it with 400grit sand paper then clean it and be done? Is there anything I should ask him to spray to make sure paint doesnt peel off, I have no clue since this is my first time getting my side skirts painted

 

since it's a plastic part never use dry sand paper. Always use WET!
make sure to use a fair amount of water when sanding.

if there is a ton of layers of paint you may need 400 wet > 600 > 800
I would advise to try and not use 400. do a test area and see how 600 sands. if you are going nowhere fast try 400

if there is just one coat of paint = 600 wet then 800 wet
and if there is no paint just hit it with 800 wet

Your final grit should be 800 wet that is optimal for a painter to shoot.

good luck

 

you can dry sand on plastic pieces just to scuff them up and clean off any dirt/grease a little easier, but then wet sand afterwards. I normally use 600 grit paper when wet sanding before painting parts. Be sure to ask him to spray a paint adhessive so that the paint will stick better

 

would these same steps be used on a brand new unpainted bumper?

 

a lot of people just use a scuff pad but yes it would be 800 wet.

plastic parts
primer - 400 wet
base - 800 wet

 

there is a difference in between 600 and 800 grit. 600 will leave too many scratches that quite possibly will show through when you paint. if you like scratches under your paint then power to you.

 

work smarter, not harder.

painted or not, just clean, degrease, clean, scuff it with a grey scotchbrite. and clean again. and have it painted.

 

Yes, these steps can be used for bumpers as well

I haven't had any issues with using 600 grit, but remember, every body man is different, so if 800 is your preference, then use it.

 

unpainted bumpers are different, some bumpers (oem honda and toyota) you need to sweat out. which is to leave in the paint both for a bake cycle and if you dont have that scuff with a grey scotch brite and hot water (not boiling, hot at the touch) with some dawn soap.

aftermarket bumpers dont need that and any bumper with paint on it should be a scuff and shoot given no signs of paint failure.

grey scotch brite some dish soap and water.

 

if they are raw plastic you need to go to lowes and buy some tsp from the paint dept.. mix it into hot water and using a red scotchbrite pad scrub and clean the sideskirts. then you need to clean them with warm water, scuff stuff or scuff and clean, and a red scotchbrite. DO NOT LET THE SCUFF STUFF DRY ON THE PLASTIC, keep it rinsed off when done. then blow it dry or allow it to air dry, wipe it clean with a leather and plastic prep and spray it all with a light coat of bulldog or other plastic adhesion promoter according to directions on can. once dry, spray with 3 coats of a real primer(not can or laquer) allowing to flash between coats. let dry and then wet sand with 400 or 600. do not break through to the plastic, if you do you will need re prime those areas and wet sand again. any areas that you break through will leave tiny furry looking sections in the plastic that will show through the sealer/base/clear.

ppg also sells a kit called one choice or 1st choice( i cant remember) that contains everything in one setup to prep plastics also.

 

now if they are painted you can just clean them with hot water, scuff stuff and a red scotchbrite. once again not letting the scuff stuff dry on the part. then they can just be cleaned and sprayed.

 

if the side skirts are factory ones or they are aftermarket urethane kind, i would wetsand them with 220 grit. 400 will do ok but it take you alot longer. start with 220>400 wet.

for plastic i would use a gray scuff pad and clean with wax/grease remover