Powder coating for "concrete"??

[Sean McLean]

I have hundreds of figurines to "paint" or finish - each about 30cm high and made of Hydrostone (a gypsum-based, cement-like material which is a finely ground white powder).

Have been using conventional aerosol spray cans (I have a professional spray painting unit, but avoid it since my spray-painting skills are minimal!) and this works, but I want to find a coating that bonds better and is more durable.

Has anyone any experience of applying powder coating to materials like concrete or even Hydrostone or similar? It's non-metallic, of course, and I understand that the object to be powder coated needs to be "electrically conductive" because the charged powder particles need to be attracted to the object. So can concrete be powder coated or not? Is there a surface coating that may be applied to make it "electrically conductive"? Or is it enough to earth the object? But then, if you "earth" a non-conductive object, only the point of attachment would be at "earth" potential - and not the rest of the surface, unless the surface was conductive? Yes? No?

I've read that now the powder-coating companies are providing powder coating for non-conductive materials such as wood and even modern composite or artificial "woods" such as chipboard and compressed board. So I'm hopeful that maybe a similar technique might apply to hydrostone...

Can anyone explain to me the physics of the problem? Or better still, just tell me it can be done - and how! Although it's nice to understand as well!

Also, is there such a thing as "flat black" in powder coating? Do not want a gloss or "enamel" finish.

Thanks!

Please post answers here but would appreciate it if you also reply to:
smpa@ozemail.com.au
(just in case I can't get to this site while travelling)

[notso]

humm interesting, have you tried sticking metal leaf into the surface?? -gold would certainly help carry a charge, but not sure what it would do to your colours?? (in terms of perminance and clarity)

-there are acid based stains out there for use with cements as well, that seems to be able to deliver vibrant colours

[iron ant]

I just returned from a powder coater several weeks ago.The finishes available are unreal,and flat black is available.First problem I see is no charge,second if your plaster has moisture in it,the oven will sweet it out or maybe crack it.I would use a concrete sealer,buy a cheap spray gun at the hardware store,flat black eqrilic enamel and you might save yourself a big headache.Spraying flat black is the easyiest finish in the world,now gloss is another story.Good luck.Oh ,also the automotive part joints sell automotive quality paint in the can,kind of expensive though....

[micahharwell]

Portland cement-based paints work _very_ well on mortar, plaster, or concrete surfaces. They are hard to find, but you can mix your own easily if you don't need exact coloring.

You'll need:
- White portland cement
- Integral color pigment for mortar or concrete
- Acrylic admixture

Mix together the pigment and cement in the proportion you need for the color you want. This is your paint powder.

Mix equal parts of paint powder and acrylic admixture (by volume).

Brush it on, or strain it and spray it on. It does dry fairly fast, you'll have anywhere from 1-5 minutes depending on surface dampness, heat, and wind.

Some people dilute the acrylic with water for a thinner paint, but more water will reduce the strength of the paint.

You should be able to find the cement and pigment at the big home improvement stores, the acrylic is harder to find but it must be one designed for use in concrete.