Wet Blasting and Getting the Black Rust Out

JimKueneman

Mopar Nut
Anyone with experience with wet blasting and getting all the rust out of panels? Is it aggressive enough to dig all the black rust deep in the pores of a panel? Would it remove this to raw metal?

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Let us know your thoughts on this unit. I have a HF pot blaster that everytime I use it I feel like im going to throw it across the yard!
EXACTLY! Professional stuff they have just the gun itself is over $1000 so I am hoping they know something about how to make a decent mid range system.
 
the issue with the cheap blasters is that they are all made with plumbing fittings. ball valves, etc. blasting is a violent process and plumbing fittings will never hold up. a good blaster will have a true mixing valve with carbide internals as well as a really heavy duty carbide nozzle. i have a marco blaster that i never use anymore and when i did it was rarely. even as little as i used it it was still worth the 3500 i paid for it over the time wasted on a cheap blaster.
 
most issues are wet air, reusing media without sifting the garbage out of it. They are all pretty simple machines. You can get a little trigger unit with a hose to put in a 5 gallon bucket for 30 bucks, then buy a new one next time you want to use it.

Big jobs, I put a tarp down, try to work on it, lift a side where you get some media back a few times, but sifting before it goes back in the bucket or pot is key.

Some of you guys in open fields can just lose the sand but us city folk gotta find a way to clean it up.
 
most issues are wet air, reusing media without sifting the garbage out of it. They are all pretty simple machines. You can get a little trigger unit with a hose to put in a 5 gallon bucket for 30 bucks, then buy a new one next time you want to use it.

Big jobs, I put a tarp down, try to work on it, lift a side where you get some media back a few times, but sifting before it goes back in the bucket or pot is key.

Some of you guys in open fields can just lose the sand but us city folk gotta find a way to clean it up.

The problem with us out in the open fields the wind blows all the time and you can't keep the tarp down!
 
My first blasting pot was a siphon feed, but I didn't get good results until getting a pressure pot. Maybe it was the brand, I couldn't say for sure.
 
Some thoughts on media.

This is some info on blasting media that I found while researching it years ago and it has worked good for me, so take it or leave it.
You want something hard enough to remove the rust, but only slightly harder than steel for blasting sheet metal. Hardness is measured in Mohs hardness, and glass is the media that meets the requirement. But glass beads are smooth and very good for polishing but won't cut through the rust, you need crushed glass with the sharp edges to cut.

Mohs HardnessAbrasive, substance or mineral
0.5–0.6sodium
1talc
1.5tin, lead, graphite
2cadmium, gypsum
2.5–3gold, silver, aluminum, zinc
3copper
3.5platinum
4iron
4–4.5steel
5apatite (tooth enamel), zirconium
5.5molybdenum, glass, cobalt
6titanium, uranium
6–7silicon, opal, silica sand
7quartz
7.5–8emerald, hardened steel, tungsten
8
8.5chromium
9
9–9.5Silicon carbide
9.5–10boron
10diamond

BENEFITS OF CRUSHED GLASS​

  • Crushed Glass will leave a clean metal surface.
  • Leaves an excellent profile for paint adhesion.
  • Glass leaves a clean white surface with very low particle embedding.
  • Weighs less than most abrasives.
  • SAFE - no free silica, non toxic, dust is classified by OSHA/NIOSH as "nuisance" dust.
  • Much less dust than coal slag blasting media, which is very helpful in the blast cabinet.
  • Mohs Hardness of 5.5
  • Superior rust-back performance when compared with mineral/slag abrasives.
  • Contains no highly toxic beryllium, like mineral slags do.
  • Uniform density.
  • 100% recycled.
Blasting with crushed glass is different from slags and other heavy abrasives, you must cut back on the media in the air stream for best results.

Start by purging your air line so it is abrasive free. Then slowly open the feed on the blast pot until you can see the abrasive in the air stream. Then slowly close the feed until you can no longer see the abrasive in the air stream. This is what you want. You may have to play with it some to get tuned in.

Blast at about 90 psi, or less. Higher pressure will be counterproductive due to how light glass abrasive is. You will simply shatter the glass rather than allow it to work for you.

Crushed glass usually comes in 3 sizes. Fine, med and coarse. You want to use med 40/70, its a perfect grit for paint and body work. Coarse is heavy and good for car frames, bridges, etc. Fine is like powder, it will slowly remove paint.

With 7.5 HP 24 CFM compressor I use 50-90 PSI, depending on the panel.

Sufficient CFM and clean dry air is essential for good results, and a compressor with less than 25 CFM of air will work best with 1/8 inch nozzle - just watch it for wear.

  • #2040 Medium Coarse. This blend of grades is great frames MIL Profile: 2.5+ on steel surfaces.
  • #40/70 Medium. Used for auto paint stripping and rust removal. (45-50 PSI when blasting low crown or flat panels like a hood, or thinner metal such as for autos from the late 90's-up) MIL Profile: 1.0 to 2.0 on steel surfaces.
  • #70/100: Fine. Great on softer metals and substrates. Excellent for etching and de-greasing on aluminum. Works as a good substitute for soda blasting. MIL Profile: 0.5 to 1.0 on steel surfaces.
One mil is .001 inch
Distance and angle of the nozzle also makes a difference.
 
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