Blasting media to restore as cast finish to alloy?

[KnightEngines]

Doing some restoration work, a lot of the alloy castings have been previously glass bead blasted.
I'm looking for a blasting media that'll work in my glass bead cabinet & close up the pores of the alloy to restore a closer to "as cast" finish.

Small steel shot?
Larger glass bead?
Plastic bead?

Fresh glass bead comes close to the finish I want, but not close enough!

[4vpc]

There are many different sizes of glass bead which all give different finishes, you could try sand too - at least it's cheap for testing purposes.

[Calypso]

Vapour blasting seems to give nice results. Several youtube videos about that and nice pictures from google search. A local guy built his own setup picking features from different videos and gets nice results. He uses glass "crush" as media mixed with water.

Although not sure if it's a solution to exactly what you are asking about...

[BillK]

the alloy castings

Are we talking about Aluminum ? Or some other alloy ?

[KnightEngines]

Aluminum.

Wet blasting works great, but won't restore an already bead blasted surface (tried it!)

I heard years ago about hard rubber shot blasting, but can't find anything on it, that'd be ideal.

[rebelrouser]

I do a little restoration, and restoring like new finish on different parts is an issue. A lot of times an old fashion wire brush on a drill does a better job than a blast cabinet. I only use a blast cabinet if the part is really corroded. I have an assortment of wire brushes for a drill and a really stiff brush on a grinder motor, most of the time the brushed finish is the closest to as new. And there is specialty paints and coatings.
On transmission cases for example, I have just went to cleaning and using a cast blast type paint. Eastwood has a lot of specialty paints to restore an as new look to parts. But I guess it depends what level you are restoring to. I have seen some real picky restorations.

[Walter R. Malik]

Doing some restoration work, a lot of the alloy castings have been previously glass bead blasted.
I'm looking for a blasting media that'll work in my glass bead cabinet & close up the pores of the alloy to restore a closer to "as cast" finish.

Small steel shot?
Larger glass bead?
Plastic bead?

Fresh glass bead comes close to the finish I want, but not close enough!

The media blasting shop around here who does my big blasting jobs uses Walnut shells.

[dannobee]

If you want a true "as cast" finish, I don't think any kind of media blasting will do it. I've tried most of them. IMHO, if you want it to look brand new, as in right out of the box or right from the foundry, it'll be a chemical with phosphoric acid, but you need to try it on a small area and adjust the time to leave it on. Go to WalMart and buy some chrome wheel cleaner (I think they carry Meguires). You want the strong stuff that etches aluminum. Try it first on a test piece to get used to the process. Wear gloves and use a stiff bristle brush. It will NOT work on magnesium, it'll just turn it a dark grey.

[BCjohnny]

Small round steel shot, S230 or close ...... won't be exact but as close as you'll get

DO NOT used 'chopped' steel shot by mistake

[BCjohnny]

Suspension parts I did a couple of weeks ago with S230, red rusty prior ..... airless blaster though

[BCjohnny]

Aluminium rocker cover S230

[David Redszus]

Small round steel shot, S230 or close ...... won't be exact but as close as you'll get

I have found the same . Sand blasting leaves a dull finish due to the sharp edges of the silicon crystals.
Shot peening can sometime leave an oily finish if the shot is not brand new.

Aluminum castings can be either die castings or sand castings; they have different surface finishes.
Surface corrosion will also affect the visual appearance of cast surfaces.

After you have blasted the surface clean of any oxides, it must be protected against further corrosion
which can occur quite rapidly. I generally use clear Alodine (not anodize) as a surface protectorant followed by
clear Ceracote.

[Sparksalot]

Recreating an as cast finish with a media blasting operation is a lost cause. It simply doesn't work. It's also why some of us old guys still do what we do.

[Joe-71]

Black Diamond, or #3 sand at low pressures will give a porous finish to aluminum. Then steel abrade at low pressure for shiny, new look. Joe-71

[dannobee]

This was done using chrome wheel cleaner with phosphoric acid. It had the greasy crap and corrosion before. No media blasting, just the cleaner.