sanding/primering roof

[dikdiamond]

I have several spots on my roof,about the size of a nickel,where the paint has bubbled and broke open and started to rust. What steps can I take to sand and primer it black? Not sure what grit of sandpaper to use,and if I should sand down the whole roof and primer it(rust spots aren't all over it,just certain areas). And should I take the paint completely off? I'm not planning on repainting it for a bit,just going to leave it flat black. Weird that my roof would be the first place to rust,even checked under the trim pieces and no rust yet...a little oxidation but what 16yr old vehicle doesn't have that

*SIGH* nobody has done any body work to any kind of car,or sanded off rust? Honestly I never have,and when I search here or on the 'net I get different opinions as far as sandpapaer grit,sanding the surface down to bare metal,etc. Here are some pics...

<a href="http://photobucket.com" target="_blank"><img src="http://i31.photobucket.com/albums/c355/dikdiamond/roof2.jpg" border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>

<a href="http://photobucket.com" target="_blank"><img src="http://i31.photobucket.com/albums/c355/dikdiamond/roof1.jpg" border="0" alt="Photo Sharing and Video Hosting at Photobucket"></a>

[Do not bump your threads.]

 

[TURBOKIDD90GST]

i would sand the entire roof just to keep it from spreading. start of with 320grit on the rust spots. make sure you get all the rust gone. once that is done sand the remaining roof with 600. put primer over that sand with 600 primer sand with 600 then put 2 or 3 top coats of flat black. make sure to clean of the roof before and after each sanding process.

 

[dikdiamond]

Thanks TURBOKIDD90GST,that's the direction I've needed. My plan is to get the entire car painted next year but the roof needs fixed now,as you can see.

 

[roadrunner2176]

TURBOKIDD90GST has some good info. 320 would take you forever to sand it down, and if the rust is pitting your going to have to fill them anyway. I would start with an 80-100 to sand off the clear and step it up from there when you hit the paint. If you don't have an air sander you could use an angle grinder with flex wheels or a flap wheel. or a regular 1/4 or half sheet palm sander. If you use the angle grinder method be careful that you don't get to aggressive a grit. Your going to have to spend some time on each rust spot, grinding out the rust and leveling the divots. (fill with a leveling compound) After you've leveled things off, use some cheap flat black paint and lightly spray the hood. Grab some 220 sandpaper and block sand until the black paint is gone. Wherever you see black paint left you will need to either fill or level. Do this until you sand everything down and don't see any paint left. From here you can spray your primer. You want thin coats, so don't spray one heavy coat. Keep things clean and smooth when spraying and you shouldn't have any problems.