Painting plastic components

[Manotea]

I've got some smallish plastic bike components I'd like to restore to pristine glory with a coat of silver paint. Whats the best/cheapest way to apply a durable finish?

[fruitcake]

If the plastic is at all flexible, I'd say go for acrylic paint, which should resist cracking.

[Brucey]

depends on the plastic, and whether the paint you apply has to stick to the plastic itself or an intact (but scruffy) extant paint film.

 Plastic primers typically contain solvents that briefly attack the plastic enough to make the paint stick. The required solvents vary in type and amount for different plastics.

So if you know what plastic you are dealing with, you can choose accordingly. Otherwise it is a matter of carrying out tests with various paints to see what works best.

cheers

[Jurek]

If the components are injection moulded and recent, there's a good chance that they'll have recycling information stamped on them which usually identifires the material.
PP - Polypropylene
HIPS - High-Impact Polystyrene
PS - Polystyrene

and so on.

ETA - Why not have them Vacuum metallised? It'll look a million times better than paint ever will.

[Torslanda]

I recently restored some STi front caps from a pair of Tiagra levers (4400) that are obsolete.

Rub down, 2 coats of etch primer, several coats of grey metallic, several coats of lacquer. All acrylic from Hycote as matching brands is the best way to eliminate any chance of reaction.

All done quite quickly but dried off after every coat by a 2kw fan heater. A method I've used before for both plastic and metal components, place the painted parts in the vicinity of the heater, not on it or directly in the air stream.

Using solvent based paint obviously means risking the paint melting the plastic but you need to be pretty ham fisted for this to happen. As long as your first coats are delivered from a distance - say 45-60cm - it's unlikely the surface will get 'wet' enough for a serious reaction. Warming your aerosols first helps too.

[Manotea]

I recently restored some STi front caps from a pair of Tiagra levers (4400) that are obsolete.

... which in fact is exactly what I had in mind.  Though the cost of the primer, paint and lacquers (and the thimbleful I'll actually use) is making me wince.

... I suspect I'll be resorting to the silver paint from my old airfix kit.

... or mebbe take them along when I next get my nails done for a coat of shellac.