Sandblasting Automotive sheet metal

Diesel_Brad · Mar 25, 2017

hey guys, what is the best way to blast automotive sheet metal with out warping it?

I have heard lower psi, blast from far away, blast at an angle, Don't use sand, etc.

But from guys who actually blast automotive sheet metal..... What works? Ans what doesnt

rustyjames · Mar 25, 2017

Personally, I would never use sand on a car body, the sand goes in all kinds of nooks and crannies and provides a nice environment for moisture to collect, leading to rust. For paint removal on vehicles I always used a chemical stripper, being careful to mask off areas that I didn't want it to go, like seams and jambs. Most shops going with the blast method typically use a media other than sand.

Diesel_Brad · Mar 25, 2017

Chemical stripper does Nothing for rust though

And as long as you srtip a car first, then it doesnt matter where the sand goes

rustyjames · Mar 25, 2017

Agreed, on stripper not doing anything for rust. For that I used Metal Prep (phosphoric acid). My method using it was to cover the area with soaked paper towels, keeping it wet, and hitting every now and then with a wire brush. Didn't take much effort to wind up with rust removed.

Blasting is fine on panels, I was referring to parts where the sand can enter, but a pain to remove such as unibody boxed parts, such as a sub frame, or underside of a hood, etc.

I've hit rusty sheet metal with sand, just kept the feed higher, lower pressure and further distance. I never tried it on a flat hood, or deck lid though because of the fear of warping the panel.

nonobadog · Mar 27, 2017

I media blast cars. I have 1 body shop and 2 custom shops that I do regular work for. I use #70 silica or crushed glass, #5 nozzle @70psi for most of the vehicle. On hoods I tend to lower the pressure to 50psi. For thin metal like old coach style bodies I use #105 or walnut shell and 50psi.

Be aware of the danger of using silica. I use fresh air helmet and thoroughly clean the parts before they leave the booth. For me silica is less than 1/4 the cost of any other media. There are new standards of silica exposure.

Do not try to clean in one pass. Keep the nozzle moving and at an angle. I use about 30deg. I have warped one panel and that was a hood. I forgot to lower the pressure.

I have also used soda and urea because that is what the customer wanted.

If you have never done automotive panels you could get some parts to practice on cheaper than ruining a customers job. Play with the pressure, angle and volume of grit to see what works for you.

Diesel_Brad · Mar 27, 2017

nonobadog said:
I media blast cars. I have 1 body shop and 2 custom shops that I do regular work for. I use #70 silica or crushed glass, #5 nozzle @70psi for most of the vehicle. On hoods I tend to lower the pressure to 50psi. For thin metal like old coach style bodies I use #105 or walnut shell and 50psi.

Be aware of the danger of using silica. I use fresh air helmet and thoroughly clean the parts before they leave the booth. For me silica is less than 1/4 the cost of any other media. There are new standards of silica exposure.

Do not try to clean in one pass. Keep the nozzle moving and at an angle. I use about 30deg. I have warped one panel and that was a hood. I forgot to lower the pressure.

I have also used soda and urea because that is what the customer wanted.

If you have never done automotive panels you could get some parts to practice on cheaper than ruining a customers job. Play with the pressure, angle and volume of grit to see what works for you.

Thank you for your experienced answer. I have a fresh air system so no worries with the silica

nonobadog · Dec 20, 2017

When done properly sandblasting does not damage the metal. Yes it does take some metal off to leave a good patina for holding paint.

The painters I know power sand metal with a course grit before painting for adhesion. When I am done blasting my guys usually just wipe it down with solvent, a tack cloth and apply sealer. No need to sand. I am not a painter, but this is the feedback I get from my customers.

Most of the dippers are gone due to EPA. Shipping to and from those left can be killer for hoods fenders trunk lids etc.

BlueDog · Dec 22, 2017

nonobadog,
Have you done any wet blasting for automotive? That seems to be catching on a lot out this way. I have a few customers that are loving it because the water helps with the warping.

nonobadog · Dec 22, 2017

I have not. I have heard a lot of pro and con to wet blasting. There are several informed discussions here on the forum.

The machines are expensive. You have to put an additive in the water to keep the metal from rusting right away. I have heard the cleanup can be nasty. The grit is one time use only.

You can use more pressure and work faster with no warping or dust.

I have thought about trying a winn nozzle but have not decided to make the investment yet.

BlueDog · Dec 27, 2017

The machines are expensive, no argument there. And of course, some are more expensive than others. We sell the Greener Blast machines for around 30k. You do have to run Holdtight 102 or another rust inhibitor so you don't flash rust right away and that stuff isn't cheap either. About the only place you "save" is time. I've seen guys strip a car in no time with these machines.
The water induction nozzle is certainly a little easier on the pocket book to give a try. We carry them on the site for around $285-$340. I haven't had any feedback yet, but I did have a guy come in and grab one. He said he loves using them, but I don't remember what he was blasting! If you use one on this application, please let me know how it works.

Sandblasting Automotive sheet metal

Diesel_Brad

rustyjames

Diesel_Brad

rustyjames

nonobadog

Diesel_Brad

nonobadog

BlueDog

nonobadog

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