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bitor 12-23-2006 05:07 AM

black sand
I am media blasting using this black sand (black beauty?) medium grit. I am blasting with 90psi on a spot blaster and trying to get rust out of surface rusted but heavily pitted metal. I blast it but when I go and use picklex (rust converter) I can still see black marks deep inside the pits! What am I doing wrong? Is black beauty too big to get in there and remove rusted metal? What can I do?

poncho62 12-23-2006 05:36 AM

Possibly, but you are never going to get every speck of rust out of those holes either. The best way is to replace the metal with new stuff.

bitor 12-23-2006 05:53 AM

lol that's not an option!

adtkart 12-23-2006 07:00 AM

Have you read the post by Randy Ferguson on rust removal? I think it is in the Knowledge Base. It is very informative!


oldred 12-23-2006 07:16 AM

Aluminum oxide or plain play sand does a really good job of removing the rust and will probably reach the bottom of those pits, just wear a GOOD respirator.

bitor 12-23-2006 07:18 AM

I have got a bag of aluminum oxide left, just stopped using it because it was too expensive. Is 90psi ok for my case?

oldred 12-23-2006 07:33 AM

90 PSI should be ok but since I am not sure what you are blasting and what equipment you have I would only be guessing. You said spot blaster so I assumed you were talking about small spots but if this is a large flat area and you are using a blaster, either suction or pressure, that covers large areas then the sand would be a bad idea because of the danger of warpage. How big an area are we talking about?

bitor 12-23-2006 07:39 AM
Mostly seams and overlapped areas.
that's my blasting gun.

poncho62 12-23-2006 07:59 AM

I have a small spot blasting gun, that has a canister and a bag on it........It reclaims better than 50% of the media..........less mess and you can reuse it.

oldred 12-23-2006 08:13 AM

Max pressure the blaster is rated for and warpage should be no problem there, respirator- :thumbup:

shine 12-23-2006 08:25 AM

90 psi is gonna warp stuff pretty bad. i use starblast because it is very fine and will clean the pits out. leaves a good anchor pattern and it is very forgiving on warpage too. NEVER shoot 90 degrees at a panel or it's going to wave bye bye . blasting can be done with 40 psi with no problems. my rig runs at about 40 psi .

ps.......... playsand kills.

oldred 12-23-2006 09:36 AM

I use 90 PSI and higher with a pressure blaster all the time on seams such as that and warpage does not seem to be a problem, I don't think it would be on those parts in the pics either. I have had some serious warpage problems in the past but that was on flat surfaces and I have warned repeatedly about that. I have found aluminum oxide to work extremely well in removing rust from pits and in fact it works especially well on separated seams where the rust is usually quite deep.

ps play sand makes you miserable for a while and then it kills.

shine 12-23-2006 09:43 AM

i agree red. it's flat panels where you get into trouble. door edges get folks in trouble. doing door jambs and hitting the edges a little will warp a 1/4 panel in a heartbeat. my rig is a little bigger. i have a 1 1/4 hose with a 3/8 nozzle. i have a 185 cfm compressor but only use around 40 psi. try the starblast sometime. it's very fine and has less the 5% silica. only 10 bucks a bag.

Bee4Me 12-23-2006 10:00 AM

You just have to keep at it with the coal slag.
It will eventually clean it up and using it on areas other than panels is not a problem IMO. I'm using it myself on the current project and it actually cut's better after a couple cycles as it breaks down and gets into a smaller area.
The media as it first comes out is rather large and most of it bounces off and WAY out into the area so a tarp is necessary to recycle it. After it breaks down some it will be easier to contain and recycle.Just be sure to clean the greasy gunk off first as well as the seam sealer cause it can get recycled into the next blast and gum up the metal with the residue causing you a world of trouble later down the road with the paint.The blaster nozzle is another concern as some have a very large opening and put out a lot of material which is fine for lots of area fast but deep rust needs a smaller nozzle to concentrate the media to exactly where you need it. If the pitting is "that" bad,the metal needs replacing anyway. Here is the firewall/cowl seam which is "toast" in most of the seam area but still some good metal left on the firewall. I'm having to "cut & paste" as no replacement panel is to be found which is a shame cause most all these 80's trucks are wasted here.
Here I have blasted the firewall and sanded the cowl. Most of this will get replaced with new metal but I wanted it clean to SEE how bad it really is,which is coming to "light" after the blasting. :(
After cutting out the bad metal I made patchs using a stretcher tool and round pipe to form the repop part along with a little work with the hammer.

oldred 12-23-2006 10:41 AM

Bee, That warning about contaminating the sand/media with sealer, oil, grease and undercoating is one that is not mentioned enough. Some years ago I recycled some sand that I had used to blast the underside with after scraping as much old undercoating off as I could but the tar (or whatever that crap is) wound up embedded in the metal surface where it caused some real headaches. It is not as simple as wiping it down afterword because the rough surface makes it a bear to remove and if you don't get it ALL- :pain:

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