Epoxy over sandblaster metal

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PostPosted: Thu Oct 26, 2017 2:58 pm
The crystalline turns to micro dust from the impact with the part due to the velocity with which it hits the part. That's what causes the danger. That's not happening when you are out in the dunes. It is what's happening when you are media blasting. Duning? OK! Blasting with raw silica sand very not OK.

I don't know of any commercial blasting media distributor that still sells silica based media. Any sand you use has silica. That's what makes it sand. :D In the cabinet I use aluminum oxide or glass of varying mesh in addition to a soda blaster for more delicate jobs. I've also used waterjet garnet in the cabinet at Techshop. At that time they tried to save money by using the same garnet in the cabinet that they use in the waterjet.

For apps where I don't need to abrade material but remove coatings (not rust) I've moved to chemical strippers. They also work well for big parts that either can't fit in the cabinet or have other things attached where you can't hit it with a hopper pot. I've been using Benco Ben 15 semi paste for brush on and Ben 17 for dipping. They make the aircraft stripper from Klean Strip look like a toy. The downside is they are a carcinogen and hazardous corrosive. Auto paint comes off near instantly and powder coat peels up in a couple of minutes, no problem. If I need to abrade it for coating I hit it with the appropriate grit DA after the previous coating is removed.

https://www.bencosales.com/powder-coati ... -strippers

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PostPosted: Wed Nov 08, 2017 10:25 pm
I was reading ********** epoxy tech sheets the other day and I think they recommended sanding it too. Also if you soda blast, they suggest to use a neutralizer.



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PostPosted: Thu Nov 09, 2017 6:40 pm
sportbikepainter wrote:I was reading ********** epoxy tech sheets the other day and I think they recommended sanding it too. Also if you soda blast, they suggest to use a neutralizer.

********** does not mention blasting profile, only sanding with 80 grit; which is the industry standard prior to epoxy application. Since 1984 and after blasting with 000 silica or other media, I've gone directly to epoxy with no sanding. Everyone I know in this business does the same. Otherwise the surface gets sanded with 80 grit, changing the paper often and not being cheap about throwing dull paper in the garbage.
Yes you can still get silica sand by the pallet load here sold by commercial suppliers who also sell other media. Most pro blasters have been using it for decades, run a commercial blasting system, and wear a fresh air supplied respirator.
Soda leaves a residue; far too many media choices available today that outperform it.

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PostPosted: Sat Nov 11, 2017 10:05 pm
What's the difference in how you get to the bare metal? Does sandblasting metal "scratch" it enough for mechanical adhesion? Wondering bc I'm considering getting the cab on my '30 Ford truck blasted.



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PostPosted: Sat Nov 11, 2017 11:24 pm
sportbikepainter wrote:What's the difference in how you get to the bare metal? Does sandblasting metal "scratch" it enough for mechanical adhesion? Wondering bc I'm considering getting the cab on my '30 Ford truck blasted.


Having the car blasted is a normal part of the restoration process. They'll have it blasted then covered with epoxy primer as soon as possible to avoid flash rust. If you need to work on the raw metal you can remove the primer or do light mud over the top of the primer.

The amount that is cut from the material is called a "profile". The coarseness of the media will determine the profile. For example a coating I use on the off road truck calls for either a 36 grit mechanical sanding or a 2 mil anchor from blasting. I've used it both ways. The media blasted method works best. To get the a 2 mil profile I use 25-40 sieve glass. For something that calls for 80 grit a 70-140 sieve would be more appropriate.

This has some basics on media size and profile.
http://blastjournal.com/how-to-choose-t ... -abrasive/



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PostPosted: Sat Nov 11, 2017 11:35 pm
ScottB wrote:Yes you can still get silica sand by the pallet load here sold by commercial suppliers who also sell other media. Most pro blasters have been using it for decades, run a commercial blasting system, and wear a fresh air supplied respirator.




Sure that's not Olivine or another kind of low silica mineral sand? Those look and blast like playground sand but aren't hazardous in the same way. I haven't seen any shops big or small using playground sand in years. In the automotive realm it would be an outlier.
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