Spray-painting fiberboard (FR4)

[Stealth]

While gathering material for my first pickup wind, I've settled on a 2mm thick piece of 500 mm × 300 mm FR4 which I've asked around about, and everybody claims it should be sturdy enough. The trouble is, the FR4 I'm getting is horrendously ugly - we're talking moldy yellow color that looks like it's festering with the plague itself.

So - has anyone ever tried to spray-paint fiberboard? How would you go about it? I would assume using rough sandpaper (circa 120 grit) would be the first step to insure a rough enough surface for the primer, but what kind of primer would work on fiberglass? Also, would using auto-paint spray work? I was considering going with basic black or graphite grey.

[jonson]

Fibreglass material as in boats and cars etc is paintable with anything. No need for acid etch primers or anything special. If it is raw material then their is a certain amount of paraffin wax (kerosine) mixed in to rise to the surface to form a barrier so the resin dries, so that does need good sanding but no more really that 220 grit. Cellulose, 2 pack acrylics, Polyurethanes and polyesters are all good as is their primers and for what you want some aerosol cans from the autobody shop will be fine.

[Joe Gwinn]

Originally Posted by Stealth

While gathering material for my first pickup wind, I've settled on a 2mm thick piece of 500 mm × 300 mm FR4 which I've asked around about, and everybody claims it should be sturdy enough. The trouble is, the FR4 I'm getting is horrendously ugly - we're talking moldy yellow color that looks like it's festering with the plague itself.

So - has anyone ever tried to spray-paint fiberboard? How would you go about it? I would assume using rough sandpaper (circa 120 grit) would be the first step to ensure a rough enough surface for the primer, but what kind of primer would work on fiberglass? Also, would using auto-paint spray work? I was considering going with basic black or graphite grey.

Painting FR4 is easy, but wet sanding the surface to be painted is advisable, both to remove all traces of mold release from the surface and to roughen the surface to improve paint adhesion. The reason to wet sand is that the dust is very annoying. I would sand the whole sheet at once, before cutting the bobbin plates out, as one big sheet is easier to handle than lots of little pieces. After assembly, remove stray oil et al with an acetone soaked rag. As for priming, follow paint manufacturer's advice.

As for paint, any solvent-based enamel will work. Or, one can get very good paints intended for fiberglass from boat equipment suppliers such as West Marine.

By the way, FR4 isn't fiberboard (which is always cellulose based), FR4 is glass-epoxy.

[David Schwab]

I use it on the backs of my pickups and paint it black. I use epoxy spray enamel, but any good paint should do.

[Stealth]

My thanks for the info, and pardon for the bad terminology - this is indeed FR4 (glass-epoxy) board, not fiberboard as I mentioned in the thread topic.

[RedHouse]

Sure it's easy, get them clean and preped first though.

Here is a Rick clone I made.

The only reason for the self-etching primer on the top was because I left some copper on there to later help in shielding.
(been doing that on a lot of single coils lately)

The trick was to use high temp engine paint, apply it to the bobbin/flatwork, then bake it in the oven at 250° for about 4 hours. This way the paint is as hard as it will get and resists pick-scrape as much as it can.

(let cool before serving )

[Stealth]

Hey, RedHouse,

I remember your method - I was the one who emailed you about the webpage not showing up properly a few months ago! I'll see what can be done about the high-temp baking trick and hopefully that'll give the bobbins that nice black coat.