Previously blasted, now rusty. Sand it?

6

612ride

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I have a Humvee that I am getting ready to apply SPI epoxy on. It was blasted and then had to be pulled outside for 2 days and it rained. Went back in my shop and sat for a year and a half. I shouldn’t have blasted it until I was ready, but didn’t know enough then. I tried an orbital sander yesterday with a 40 grit disc. It was already on it and I thought, what the heck, I’ll use this one up. You can see in the picture how it turned out. It wore through a disc in that small of an area. I was applying some pressure.
My questions:
Will sanding it down be good enough, or do I need to blast it again?
Should I be taking it down farther?
Could I use a belt sander, to knock it down faster. Most of the areas are flat.
Would one of those drum sanders, like Eastwood and Porter cable make, work better or easier than a DA?

If what I’m doing is fine, what other prep should I be doing before priming?
Do I wipe it down with SPI 700?
How quickly does it need to be primed?
I can’t see myself getting all of the sanding done, and priming, in the same day. I’m 57.
Would I be better off doing it in sections?
I know if I do it in sections, I have to worry about the 7 day timeframe.
I know this is a long post, but I don’t want to screw this up. Thank you in advance.
 

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I'd hit it with a 3M strip it wheel, then 80 grit on da, then straight to epoxy.
 
If it were me I'd first try my hand at sanding and see how well it was working/how much patience I had with it. If it's just not there, then I'd take a red scotch brite and a phosphoric acid treatment and work just one panel at a time, scrub it down. With the help of the scotch brite it will dissolve the rust pretty quickly and scrub it away. Then while the metal is still wet, wipe it down several times with a wet rag and clean water to remove any acid residue. Immediately blow dry the panel. A quick scuff will remove any of the golden hue of flash rust that might form. Then go to epoxy.

I've done it both way, sand or acid.
 
'68 Coronet R/T said:
You might try one of these: https://www.mscdirect.com/product/details/00222760
I have found they work very well for clean up. DA with 80 after and you will be ready for epoxy.
Click to expand...
I have used those on a small hand held grinder and they work great. They do get used up pretty quick though. I’ve found them hard to keep flat on the surface also. I’ve had a hard time keeping them from catching the edge and digging in. That’s why I was wondering about using a belt sander.
 
Lizer said:
If it were me I'd first try my hand at sanding and see how well it was working/how much patience I had with it. If it's just not there, then I'd take a red scotch brite and a phosphoric acid treatment and work just one panel at a time, scrub it down. With the help of the scotch brite it will dissolve the rust pretty quickly and scrub it away. Then while the metal is still wet, wipe it down several times with a wet rag and clean water to remove any acid residue. Immediately blow dry the panel. A quick scuff will remove any of the golden hue of flash rust that might form. Then go to epoxy.

I've done it both way, sand or acid.
Click to expand...
Let’s say that I get it all sanded down in one day and then it is 3-4 before I epoxy, will I need to do anything to the surface before I epoxy? My shop is at a constancy 44% humidity. After I sand it, do I need to wipe it down, to get rid of all of the dust, or can I just blow it off with air? I’m a little unsure of the process with using anything after bare metal.
 
I blow it off well, wipe it down with a dry rag to remove any excess dust, then wipe down with wax and grease remover.
 
Imo, if you DON'T put it Outside again in the rain,
Take your Time and DA it and whatever to get the nooks and crannies done. Then Epoxy as you wish. No need to get in a hurry because you will probably be sanding and respraying epoxy anyway. Just how it is .
The Last thing would be a belt sander. Even though it's "flat", it won't be after a few passes with It.
Bare metal is generally no problem "as is" INSIDE unless you introduce Water of some sort on It.
Porter Cable has a great Electric da if you're interested. I got one years ago because it's a Lot cheaper than my Air Compressor to run. Has extra counterweight for a 6"pad too.

 
Last edited:
MikeK said:
Imo, if you DON'T put it Outside again in the rain,
Take your Time and DA it and whatever to get the nooks and crannies done. Then Epoxy as you wish. No need to get in a hurry because you will probably be sanding and respraying epoxy anyway. Just how it is .
The Last thing would be a belt sander. Even though it's "flat", it won't be after a few passes with It.
Bare metal is generally no problem "as is" INSIDE unless you introduce Water of some sort on It.
Porter Cable has a great Electric da if you're interested. I got one years ago because it's a Lot cheaper than my Air Compressor to run. Has extra counterweight for a 6"pad too.

Click to expand...
Thank you!
 
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