Bead Blasting? How-to

[LakeRacer99]

OK, I just got a bead blast cabinet from Harbor Freight. I am wanting to clean the paint of some of my outboards prior to painting them. I am in the dark on this and have no clue what to use for media. I understand that walnut shells are fragile and won't damage the aluminum, but will they remove paint? I think that might work well on bare aluminum.
What about glass beads and aluminum oxide pellets?
Are there any sites on the net with help?
Thanks for the help.

[chris_lacey]

Not sure about the very best medium to use, BUT, if you use glass beads on a internally threaded part, be sure to blow out the threaded holes and chase the threads. Lost a set of Harley head gaskets 'cause no one told me.

[beko21]

Jason, a friend of mine just had his exhaust housing blasted to paint it and the blaster used plastic media, he said the factory paint was some tough stuff but it came clean as a whistle, Kevin

[ken medendorp]

Baking soda works good I've read in auto body books where they use soda because it dosen't warp the body panels.I had also used it on my engine cases on my snowmobile.But you really have to wash parts up good after ,because it get's into everything

[2scoops]

I have all kinds of stuff blasted,On your aluminum parts I would use a fine medium like glass bead or fine sand,Both will leave the parts with the perfect texture to apply an epoxy primer/sealer like PPG DP90LF which is an excellent product.DP90 is black in color assuming that your going to paint your parts black right?They also have different colors as well.You can topcoat right over the DP without resanding provided its in the alotted time frame.

[Wile E. Coyote]

Aluminum Oxide and glass are abrasive an will remove base material as well as the anodize or alodine finish. Try using Plastic media. It comes in different grades, I think we use 30/40 grade and it works relatively well... Be sure your cabinet is cleaned of all the old media before you add new....the mix of medias can play havoc with surface finish.

[dragonwolfe]

In some applications. I previously sold the Armex/Accustrip system from Arm & Hammer. This uses a specially formulated media composed of baking soda.
This machine could actually strip the paint off an aluminum pop can at 75psi, unheard of in the industry.
We sold Kellogs some equipment to blast the cooking trays in the cereal plant, they were using walnut shells, as they are environmentally friendly.
I've seen it remove paint off a truck wheel hub at low blasting pressure that previously required 6000 psi high pressure water.
What kind of blast pressure is does your equipment operate at?

[BarryStrawn]

If you can't find blast media locally, try http://www.tptools.com/dept.asp?dept_id=12&dept_focus=143&from_header=yes

[Kajun]

Hello
I use sand in a med. grade but before i put it in the blast cabinet i pour it through a screen to get the big stuff out. Fine sand breaks down to fast. Another thing you will need is a vaccuum system. After sanding a few big pieces i change the sand or the dust gets to bad. I use about 5 quarts of sand in the cabinet at a time. I lay a piece of screen in the cabinet then pour the sand over it using a old butter bowl. Then i take the screen out and begin blasting. This works very well for me and give the parts a satin finish. Just blowing off the parts with air does not clean them that good so be sure and use dish washing soap and water to clean them. After i wash them good i run water over the whole part to get any sand left off the parts. Then i use the air to get the sand out of the holes and cracks and wash it down again. Hope this helps you.

[Raceman]

I've got several blast cabinets and keep em set up with glass beads and a dedicted one with zinc oxide. Both are available at Harbor Freight about as cheap as you can find it anywhere. I use the glass for alum stuff and zinc oxide for steel, especially when it's rusty.

Sand is much more dangerous to breath than the other two and if you read the labels on your cabinet it specifically says not to use sand. The reason is that the cabinets have an intake in addition to the port for the vacuum, plus a shop vac doesn't filter good enough to make the air safe from the silica from the sand.

I've tried other medias such as Walnut shells, but found they went away too fast and the baking soda was too slow to use on anything that had any decent paint or dirt. In the case of resto stuff, like correct alum. intake finishes on old cars, there's not much of anything that can be done in a blast cabinet that's appropriate. Glass beads ruin the original aluminum finish from an originality standpoint and it's a major deduction from major judging organizations. It takes a high dollar "reskinning" process which is actually tumbling in a special media, then a chemical bath to restore correct muscle car type finishes to intakes and alternators.

The plastic media is fine for blasting sheet metal where warpage is a problem with sand. I don't think it's practical for engine parts because of the time involved compared to glass beads.

As far as pressure, most bead manufacturers recommend from 60 to 90 PSI because the beads break down too quickly at higher pressures. I've always run mine around 90 because it seems like there's too much time involved at lower pressures. If the cabinet puts any dust at all in the air (all the low dollar ones do) wear a dusk mask at a minimum.

[LakeRacer99]

Great info so far...keep it coming. I just picked up some walnut shells to try...12-20, I figured I had to start somewhere. If it is too slow, I will step up to the glass or alumoxide which is more expensive.
I am gonna be blasting on my older outboard parts. Not gonna be entering any "Concours Events" just want it to look nice.
My cabinet is one of the cheap-o benchtop poly units from HF. Someone mentioned the static from the plastic may reach out and grab me, could I just ground the plastic?
Thanks,

[Raceman]

You can get a little static electricity from any of the cabinets that aren't grounded, and when the weather gets colder the shockin' gets worse. Two of mine sit on a wooden floor and the screws around the gloves bite pretty good in the winter. I don't know if grounding the plastic will help.

Harbor Freight runs their highest price cabinet on sale periodically for about 200 bucks (occasionally on sidewalk salefor 150) and it's a good buy then. I've also got one professional type cabinet for larger stuff, but it was expensive when I bought it and doesn't offer any real advantage for smaller stuff.

Again, it's important to watch the dust in the air. Sometimes it's hard to see, but after blasting for a while you can feel it in your nose if you don't have a dust mask on and some of this stuff does nasty stuff to your lungs, especially anything with silica.

[Techno]

Walnut shells is doing fiberglass like corvettes.
To do alumuminum you can use any blasting media you want since you aren't going to hurt the stuff.
I used black beuty, I think, on mine and it didn't do nuthin. If I held it a while I could remove a bit of casting marks but it would take a whole long time.
Your going to get a sandblasted texture if using anything aggressive but the painting should fill this in. In fact large portions of this 'fragile' item have badly cast surfaces and have terrible glitches from the get go.

I suggest forgoing the paint and sand, polish the aluminum. Too many people are painting these beutifull alluminum parts!

[jerry]

for aluminum use a 210 grit , for cast or steel use an alunimum oxide. baking soda is great for places you cant blow out completely because it will not eat up bearings ...

[heath brinkley]

Also, to save your threads, they make plastic thread savers that come in a variety of sizes, or screw some old bolts in the holes to save the threads.

[Wile E. Coyote]

Something that may or may not be overlooked here. When you blast aluminum using an agressive media, you will remove the factory applied corrosion protection barrier, i.e. the anodized finish. you will need to protect the bare aluminum before you paint it. Alodine or similar conversion coating. Paint is porus to an extent that in time corrosion will develop under your freshly painted surface.
IMO there is no substitute for the factory anodize, thus the reason for using a media that will remove the paint only.