painting undercoating
Thread Starter
Rennlist Member
Joined: Feb 2004
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From: Milwaukee, WI
painting undercoating
I am in the process of a color change for my 82 and am planning on painting inside the fender wells as the factory had. How do I prep the undercoating for paint? Do I just clean it real well with Simple Green and water and respray it? Also how about surface rust repair? In particular I am looking for recommendations of good rust inhibitors. Joe
Team Owner
Joined: May 2004
Posts: 31,239
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From: Philly PA
what is the original color and what is the new color? i would think a few cleanings of the wheel wells and then a scuff with a scotchbrite pad might do for the undercoating make sure to get off all of the old cosmoline you might try some engine gunk first to remove the cosmoline
Drifting
Joined: Jul 2004
Posts: 2,725
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From: Davidsonville, MD
I can certainly appreciate your desire to do this as thorough as possible but unless you're planning on making a concours show car, I'd skip trying to match the paint in the wheel wells. I just finished a year-long restoration on my '85 and I did paint it myself, and I did a color change on it as well. So I understand all too well about the desire to be detail oriented. But this is overkill.
Since that won't dissuade you, I guess I should offer some pointers. Simple Green can be used as a preliminary cleaner before you start any work. On painted surfaces use Simple Green followed by a silicone and wax/tar/grease remover prior to doing any sanding, masking, etc. In the wheel wells I'd use it to get the loose stuff out.
For surface rust you must eliminate the rust as much as possible. Grinding or sanding are popular methods. Then you have to treat the metal so it won't rust again. There are many products out there that do this. Almost all of them use acids. This is important to know because you cannot apply two different acid containing products over one another. So no etch primer over metals with rust treatment. You also can't apply body filler over rust converter. So after you treat the metal to prevent future rust or a return of rust, you'll need to apply an epoxy primer. Try to choose one advertised as DTM (direct to metal) or one that is chromated. Chromated primers have a greenish color. Chromates aid in adhesion to bare metal. Once the epoxy is down, you can begin the rest of your bodywork.
Since that won't dissuade you, I guess I should offer some pointers. Simple Green can be used as a preliminary cleaner before you start any work. On painted surfaces use Simple Green followed by a silicone and wax/tar/grease remover prior to doing any sanding, masking, etc. In the wheel wells I'd use it to get the loose stuff out.
For surface rust you must eliminate the rust as much as possible. Grinding or sanding are popular methods. Then you have to treat the metal so it won't rust again. There are many products out there that do this. Almost all of them use acids. This is important to know because you cannot apply two different acid containing products over one another. So no etch primer over metals with rust treatment. You also can't apply body filler over rust converter. So after you treat the metal to prevent future rust or a return of rust, you'll need to apply an epoxy primer. Try to choose one advertised as DTM (direct to metal) or one that is chromated. Chromated primers have a greenish color. Chromates aid in adhesion to bare metal. Once the epoxy is down, you can begin the rest of your bodywork.
Thread Starter
Rennlist Member
Joined: Feb 2004
Posts: 297
Likes: 0
From: Milwaukee, WI
The car is currently a light beige (don't know Porsche's name for it) and will be repainted meteormetallic or dark grey so you can see my dilemma, light fender wells, dark car. At the same time the car needs a driver's side fender so I figured that while I have everything apart I might as well paint the fender wells. Joe
