ballen
Diamond
- Joined
- Sep 25, 2011
- Location
- Garbsen, Germany
I've decided to start redoing the paint of some of my 1960s FP2 parts. The first piece is the long-reach head, which I originally took apart to clean and grease.
The paint is a 2-component polyurethane (MIPA PU 200-90). I've had it color-matched, the correct combination was RAL 7010 (Zeltgrau) with 60 grams of white added per kg.
Here is the first part I am going to paint, I've picked it because it's not very challenging, and if I screw it up, it's not going to be hard to redo. My question is, how to prep the surface?
I haven't made any attempts to do high-quality painting for forty years, since my RC model airplane days (and the materials there were typically ABS plastic, fiberglass, and wood, not cast iron). A more-experienced friend has told me that the only way to go is to sandblast the entire part free of all old paint, spray some layers of filler, sand that and then paint on top. (He says that this is also necessary because oil and cutting fluid soak into the parts, and without sandblasting everything away, the new paint won't adhere).
To me, this seems like a waste, since most of the paint and filler are intact. So I don't understand why I should remove these just to redo it. To see if this will work, I've wet sanded with 220 wet-or-dry paper, got off almost all of the obnoxious green stuff, leaving a nice scratch pattern for the new paint to adhere to.
There is no bare metal here, just lighter paint under the darker paint, then white filler under that. The parts that appear shiny actually have a good scratch pattern, but the light reflection makes it look otherwise.
(Note how the paint color has darkened over the years, from what it was under the nametag!)
Next step is to use some auto-body filler to fill twenty or so small dents and nicks (they are typically a few mm wide and deep) sand again, and then paint.
Is this approach reasonable? Or is my friend right, it's better to sand-blast off all the old paint and start over? (If my approach doesn't work well, I can always try his!)
Cheers,
Bruce
The paint is a 2-component polyurethane (MIPA PU 200-90). I've had it color-matched, the correct combination was RAL 7010 (Zeltgrau) with 60 grams of white added per kg.
Here is the first part I am going to paint, I've picked it because it's not very challenging, and if I screw it up, it's not going to be hard to redo. My question is, how to prep the surface?
I haven't made any attempts to do high-quality painting for forty years, since my RC model airplane days (and the materials there were typically ABS plastic, fiberglass, and wood, not cast iron). A more-experienced friend has told me that the only way to go is to sandblast the entire part free of all old paint, spray some layers of filler, sand that and then paint on top. (He says that this is also necessary because oil and cutting fluid soak into the parts, and without sandblasting everything away, the new paint won't adhere).
To me, this seems like a waste, since most of the paint and filler are intact. So I don't understand why I should remove these just to redo it. To see if this will work, I've wet sanded with 220 wet-or-dry paper, got off almost all of the obnoxious green stuff, leaving a nice scratch pattern for the new paint to adhere to.
There is no bare metal here, just lighter paint under the darker paint, then white filler under that. The parts that appear shiny actually have a good scratch pattern, but the light reflection makes it look otherwise.
(Note how the paint color has darkened over the years, from what it was under the nametag!)
Next step is to use some auto-body filler to fill twenty or so small dents and nicks (they are typically a few mm wide and deep) sand again, and then paint.
Is this approach reasonable? Or is my friend right, it's better to sand-blast off all the old paint and start over? (If my approach doesn't work well, I can always try his!)
Cheers,
Bruce