On my last resto I took the entire outside of the car down to bare steel. The underside and inside the trunks I just scratched it up with scotch pads (abrasive cloth). That was alot of work but it did the trick because the paint inside there was pretty good.
This car I am working on doesn't appear to have as nice a paint on the inside. Acid dipping is not an option but I was wondering if anyone has used a product that, when sprayed on and wiped clean, would etch the old paint enough to get a good adhesion to the new paint???
Full Version: Painting question - inside and underneath
Doug-
your resto project effort was pretty amazing. Thanks for the link. Oh, I don't know about the paint etching, but that is a damn fine job on the yellow car.
your resto project effort was pretty amazing. Thanks for the link. Oh, I don't know about the paint etching, but that is a damn fine job on the yellow car.
Umm, ok I'm not an expert but I have been studying bodywork alot lately and the first time I prepped my car for paint went really well, so I'll give it a shot.
Etching is only done on bare metal as far as I know, not paint. Either your existing paint is on the body well or it's not. If it flakes off like with a fingure nail test- it's no good. If it takes alot of sanding and elbo pressure to get it off- then it's on there. In that case all you need to do is a little prep to make the new paint stick to the old. You don't need to remove solid old paint- it's probably more in your favor to use it... considering it to be a stable base coat. However if it's flaking off easily- you better flake all of it off (sander time!).
For your inner surfaces which don't require a mirror finish, just good adhesion- I think you just need to clean (car wash), clean again, degrease, rough up, clean and paint. Notice the word 'clean'.
After normal washing, you would use a quality degreaser, such as something from the PPG brand. Sorry don't know the name but it will be a three digit number such as "PPG 550" for example only. After degreasing you might do a little scuff sanding to create a good 'footing' for the new paint (assuming you're not going further down the perfection road with it- i.e. block sanding, filling, block sanding, ect). Just like you did with the scotch bright pads... I used sand paper propably in the 150 (worn soft)- 320 grit range to rough up my old paint surface before priming. If you don't degrease it before you sand- then you will effectively sand the grease deaper into the paint. Degreasing is an art in itself so check out the forum below.
autobody101 forums
Etching is only done on bare metal as far as I know, not paint. Either your existing paint is on the body well or it's not. If it flakes off like with a fingure nail test- it's no good. If it takes alot of sanding and elbo pressure to get it off- then it's on there. In that case all you need to do is a little prep to make the new paint stick to the old. You don't need to remove solid old paint- it's probably more in your favor to use it... considering it to be a stable base coat. However if it's flaking off easily- you better flake all of it off (sander time!).
For your inner surfaces which don't require a mirror finish, just good adhesion- I think you just need to clean (car wash), clean again, degrease, rough up, clean and paint. Notice the word 'clean'.
After normal washing, you would use a quality degreaser, such as something from the PPG brand. Sorry don't know the name but it will be a three digit number such as "PPG 550" for example only. After degreasing you might do a little scuff sanding to create a good 'footing' for the new paint (assuming you're not going further down the perfection road with it- i.e. block sanding, filling, block sanding, ect). Just like you did with the scotch bright pads... I used sand paper propably in the 150 (worn soft)- 320 grit range to rough up my old paint surface before priming. If you don't degrease it before you sand- then you will effectively sand the grease deaper into the paint. Degreasing is an art in itself so check out the forum below.
autobody101 forums
After the prep work, try using a sealer or an adhiesion promoter before the top coat. Make sure to stick with the same product line. Mixing products is a good way to see paint failures.
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