Sandblasting advice

Try glass beads, they leave a great surface.
Ed Angell

IF you want to be able to remove the scale and other contaminants you mave need to start with sand or aluminum oxide and then work your way down to something finer. Glass bead or even baking soda. Walnut shell is amazing for cast parts or for when you want to remove contaminants but not any metal. Walnut shell will get rid of the grease etc. We would use it to remove grease, wax and clean heat exchangers etc that were not going to be painted afterwards. Worth a try.

You are not going to get white metal with softer media. Experiment with lower pressures/abrasive flows to get the results you want, using a more aggressive media like coal slag. I'd stay away from aluminum oxide due to the cost and the tendency of the particles to embed in the work. The only time you get major pitting is when the original steel is heavily rusted, which is really from the rust, not the blasting. Very light guage sheet metal would show marks but any substantial steel should look pretty smooth unless you leave the gun blasting in one spot for an extended period.

from experience beadblasting an entire aircraft.
use a rounded blast media . glass beads of a type called ballottini come in many grades.in my aircraft work I used two buckets full of them about eleven thousand times. I just swept them up and passed them through a flyscreen filter to remove the detritus. I used AH grade to good effect. water washed dry sand which is quite rounded also works really well.
the way to prevent peening of the surface is to either reduce the pressure in the airline or to direct the gun at an angle to the surface rather than perpendicular to the surface. my setup used one of those taiwanese units sold in discount auto shops. they work quite well. at 120psi the beads will remove rust and peen the surface with a finish that accepts paint really well. at about 80psi the action is gentler and at about 60 psi you can have the gun perpendicular for quite some time with just a polishing action.
btw you dont need to do all the surface at once. just bead blast the welding areas first to clean them and then after the welding is all complete go back over and finish the job.
btw the use of a single compressor is futile ( I have months of experience behind the comment) go and hire a trailer mounted compressor. these will give continuous air pressure for the duration of the job. with a home workshop compressor you will be waiting for most of the time for pumpup to occur. I thought with a 15cuft/min unit I'd be ok but to me the hand nozzles all seem to need about 60cuft/min of air. ...and the job takes forever.
the bead blasting booth bears comment as well. you only need the thinest of plastic sheets to contain the beads. I use a frame suspended from the ceiling which is draped in light weight plastic sheet paint drop cloths. when pegged up at the corners it contains the beads really well.
use air filters for your breathing air and a face mask and gloves. my face mask is an old welding helmet with a clear plastic piece in the lens. I tape a piece of transparent plastic sheet over the lens area and this takes all the abrasion. it gets replaced when it becomes frosted. Stealth Pilot

Stealth: Pressure tank? Blast cabinet? Thanks -Mike
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