Body metal replacement

[8man]

I've got a 54 cab with a decent amount of rust, bondo and fiberglass. I know I must get rid of that stuff so I can see what I have to work with. I'm going to have to replace some panels, like the lower rear cab corners and the front lower drivers side piece for sure, and maybe some others when the bondo is gone.

I'm going to have it media blasted to "strip" the bondo, fiberglass and rust away. With that done I can see the metal I'm going to work on.

I see in some shops they have the bare metal exposed while they do the patch panel replacement. Since this is a hobby, it will be weeks before I get the work done. My concern is exposed metal for a period of time.

I've read that epoxy primer as soon as it is blasted is the way to go, but then you have to remove the epoxy primer to replace a panel, and you still end up with panel joints that are not primed.

So do I prime it, or wipe it down regularly with some rust inhibitor or just leave it bare, don't worry about it, install the patch panels and re-blast any surface rust when it's ready for paint?

I'm in Bryan Texas, not as dry as AZ, but in my shop the humidity level is pretty low, if that helps.

Thanks.

[oldusafmsgt]

I'd prime it. I know here in Alabama you can actually watch bare metal rust, in real time. Not much primer has to be removed when patching, just where your welding. After grinding and finishing the weld, just spray some self etching primer on the seam.

[Jcfcamaro]

I'm no body guy by trade ,but have been doing my own rust repairs on my 72 4x4 so I can finally say I did it all. I would plan on spraying it with epoxy as soon as you get it back home. When you cut the bad spots out you can always sand the edges back to bare metal to weld . I've been doing sections at a time with my cab. And blasting it as I go with a small pot blaster. It's messy with the sand, but I can go as fast as I want with the patch replacement. A lot of times when you start cutting rust out there's more to fix then what you see and that takes more time and head scratching. A lot of my rust pieces I make by hand cutting up old doors or box sides depending on what thickness of metal I need.

[72HuggerK20]

Use weld-through primer on areas where you will be welding. 3M makes some good stuff.

[8man]

Next question.

What do you use to cut out the cab corners? I was thinking either an angle grinder or a die grinder.

I have a plasma cutter, but I can't hold it steady enough to make that straight a cut. Maybe I need to figure out how to do a better job with the plasma.

I have a reciprocating air saw that I could use and it might work, but I'm looking for some experience here.

Also, how do you mark for the cut using your preferred method? Do you draw a line, use tape or what.

Thanks.

[72HuggerK20]

Any cutoff tool works, my personal favorite being a MAC ATQP40EA. Plasma cutter will probably warp the metal. As far as marking the line, lay your patch over the existing metal, and use an awl to scribe a line along the edge of the patch. Cut a quarter inch short of that line. Make the hole fit the patch, don't try to make the patch fit the hole because it takes a lot more time. Also, I like to lap the patch behind the existing metal to make it easier to weld. You'll make up for the height difference with filler.

[oldusafmsgt]

I have a plasma cutter, air saw, air nibbler, recip saw, chop saw for certain areas For most cutting, it's an angle grinder with a cut off wheel.

[BIGglaSS]

Be patient. The better job you do to fit, the better the weld, the better the finish. Snips, air body saw, and file/grind to fit. I scribe straight lines on the patch, snip, file flat. Then transfer/scribe to the panel. I take time to fit patches zero clearance.

Lap weld joints can "ghost" in the sun. Don't do lap welds on the pretty surface.