Sheet metal prep

[decling]

I have little experience in sheet metal prep. What is the best technique sand blasting, soda blasting or crushed glass blasting. My truck is an Arizona truck so not much more than surface rust. There are some areas that have been patched poorly and then puttied over or cracks that have been brazed. Do you work out the dents first then blast? I have read that you have to neutralize after soda blasting and prime after sand blasting. I don't want to do something that causes issues later when painting.

I want to do as much of the sheet metal work as possible before turning over to someone to paint.


TIA

[19Fordy]

Can you post a few photos of what you are dealing with?

Here's some good options:
https://www.youtube.com/watch?v=ALpAnx-t1so

Also, read all threads dealing with surface rust and rust conversion here:
https://www.fordbarn.com/forum/searc...rchid=19642473

[Zeke3]

I used a heat gun to soften and remove old putty and fiberglass from old repairs. If you have cracks that have been brazed and need to be repaired, you may have to cut them out and weld in a patch. I don't think you can weld metal successfully that has been brazed. Pictures will be helpful.

[decling]

This is one of the front fenders. A previous owner had brazed on these headlight stands that are not correct. I have correct stands and headlights so I will need to get all the putty and then remove and restore to accept the originals. There is also a patch panel that I have no idea what it is covering. Then just a place that is obvious has putty. So should I media blast to see what I am working with or just start picking putty and grinding away?

[19Fordy]

Best thing to do is to first sand blast that fender nice and clean inside and out. Do not point the nozzle 90 degrees to the metal. Keep it at an angle of 45 degrees and don't warp the metal. Then you can see what you have and make needed repairs.

[Bored&Stroked]

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I would probably do all the rough metal work first - because once you blast it, you'll want to most likely epoxy primer it as fast as possible. You can put filler over quality epoxy primer (is usually the recommended way these days), but you don't want to be welding and having to redo all the primer areas.

Brazed patches - are the nemesis of all good body metal workers . . . anything with brass on it needs to go. Hopefully you can grind all the brass out - you may need patch panels that are TIG welded back in.

I prefer TIG or traditional oxy/acet for all body welding as the welds are not brittle like MIG. The most important thing with blasting is that the vendor really knows sheet metal and doesn't warp any of your panels. Take time to find the right supplier and checkout their work.

[decling]

Other front fender images

[decling]

This is the rear fender that has been brazed. They did not try to work back close to shape just put putty over it and a dent that they just put putty over.

[decling]

When I was at the Goodguys car show one of the vendors did crushed glass blasting and said it did not need primed right away as did sand blasting. The issue I had was it looked really coarse on the metal. He had pictures of multiple cars he had done for restoration. Are there pros or cons to what type of media?

[rotorwrench]

Brazzing works on some things but not so well on sheet metal. Any metal that has been brazzed would have to be removed around the soldered joints in order to perform a good weld repair. Brazzing just gets thin metal too hot and it ruins the spot for repairs or metal working. Welded repairs using RG45 filler rod with Tig or oxy acetylene are only concentrated in a small area but brazzing repairs just cover too much surface area to get the brass hot enough to melt. The brass gets into the grain of the metal and makes it impossible to weld with normal techniques.

Patches can be fabricated using hand tools if a person knows basic metal working. There are several good web sites that can be very helpful to the folks that are interested in learning all the ways to shape metal and types of sheet metal that work the best. Metal Meet is one but there are others.

Blasting requires a skill set to master as well. I've seen some parts ruined by blasters that didn't know what they were doing. There is always a way to prep metal after blasting that will eliminate problems with soda blast effects on primer adhesion. A person really needs to know the correct media and equipment to use and how to deal with the surfaces after blasting is completed. It's not something to wait around and see what happens. It has to be dealt with immediately.

[marko39]

The heavy rust needs sand blasting, the rest should be glass beads. You can do the dent removal first by block sanding after removing filler. After its down to bare metal treat it with a good metel prep before priming then proceed to the filler and more sanding. Any bare metal exposed during sanding needs to have primer. It is more difficult on rounded fenders.

[Willit Stop]

This is what I use. It will remove body filler, paint and most of the rust and will not harm the metal. Just screw it onto an angle grinder, grab the safety glasses and particle mask and go for it. They last a long time if you don't hit any sharp edges.
https://www.harborfreight.com/4-1-2-...eel-94017.html

[Willit Stop]

Here's a video stolen from youtube:
https://lugnutz65chevystepside.weebl...ive-wheel.html

[19Fordy]

Depending on the car, it might be easier and cheaper to buy a used fender. What is the year and model?

[cas3]

you may get away with sand blasting that fender as all the curves give it some strength. i would never blast anything flat, like a door or a hood, too easy to warp.

[Blastfromthepast]

Get a 6” orbital sander, use 80 grit and sand it down to the metal.
It will take longer but there’s no warping involved and
you can’t make a mistake.

[VeryTangled]

Hi Everyone! I am most definitely NOT experienced in this area. I'm asking because I'm curious.

Why not to try to chip off the filler as much as possible before moving to methods 2, 3 and 4?

That looks like low hanging fruit to me, but what do I know.

[OldGold360]

I’ve had vehicles media blasted as well as dipped. I prefer having them dipped because it removed everything and leaves clean steel. However, blasting is a good option as well but make sure whoever is doing it is experienced with automotive sheetmetal, otherwise warping can happen.

[decling]

Originally Posted by 19Fordy

Depending on the car, it might be easier and cheaper to buy a used fender. What is the year and model?

1938 Truck

[decling]

Yes, I have started to remove some of the putty since I could see it was dented to the inside. This was an area I knew needed work so a good place to check. I just through some paint on since we had a little rain the other day.