Aluminum Panel finishing - Anodizing

[vpharris]

Does anyone know how to prepare aluminum to get the rather "white" look to it when it is anodized?

A friend brought the aluminum boom to his sailboat to a shop to get anodized. He had sanded it. When he got it back, you couldn't tell that anything was done to it (though I believe it was). The sanding scratches were very shiny.

So if anodizing doesn't change the appearance in any way, how does one prepare the metal to get the whitish look that we see so often?

[Magura]

I believe its called glass ball blasting....like sand blasting, just with tiny glass balls instead.

That leaves you with the silky look.

Magura

[hifiZen]

Yeah, bead blasting. Much nicer than sand blasting IMHO because you get small, evenly sized rounded pits in the metal surface rather than the sharp nicks left by sand grains. Bead blasting gives a very smooth, uniform appearance.

[Philo]

Glass beads don't have to be the final finish if you want something even finer. There are other materials that a finishing shop can use like poly grit or walnut shells that produce a different finish. Think about using a layered looked (two pieces sandwiched together) with each piece having a different finish.

[S.C]

So blasting is the only way to solve the scratch mark prefectly ..etc etc, right? What if I use some power tool to sand it before anodize it (the aluminum plate)? Will I get good result out of it?

[Peter Daniel]

The usual finish on stereo equipment is not blasting, but brushing, either on a belt sander or the abrassive wheel.

[Philo]

Peter is correct that the usual way is brushing prior to a anodizing finish, but I (always in a rush) can get a more consistant finish with blasting than with brushing or sanding. Most of the time I get some kind of inconsistancy that bugs me everytime I look at it. To answer your original question... IMO beadblasting leaves a "whiter" looking finish. Experiment and see which one you like. All part of the fun...

[Peter Daniel]

Here's more info on brushing: brushed aluminum finish, how to?

[hifiZen]

Thanks for the link, Peter - that's some good info.

What do you think about the difference between alodine and anodize finishes in terms of durability (scratch and stain resistance)? ... and have you tried doing any type-II anodizing yourself? It looks to me like anodizing produces a tougher finish, at the loss of electrical conductivity.

Apart from the usual chemical precautions (rubber gloves, face mask/goggles, fume ventilation - the same things apply to alodining, I'm sure), anodizing looks quite simple and perhaps even cheaper than alodine. All it takes is a power supply and some battery acid. Then you have your choice of colours if you want to dye the parts. Or, you can just seal the surface by boiling in water to get a clear finish.

Have a peek at this site for detailed info on anodizing.

[hifiZen]

Second, I'd love to be able to reproduce a bead-blasted finish at home. I personally prefer a grainless finish which is really uniform and smooth... bright (white-ish), yet fairly matte just like fine bead blasting. Any ideas on how one might accomplish this without paying for a commercial bead-blasting job?