Over the years I have sandblasted many complete trucks, body panels, and frames for my neighbor who is getting too old to wrestle that hose around. Generally speaking, the hardest thing to remove is old grease...that is until I tried sandblasting the cab of my own truck. The reason? As an experiment I painted it with epoxy primer without any sort of prep work. #1 - to test out my new $10 HF purple primer gun and #2 - to see what sort of adhesion I would get to old paint. I'm telling you that stuff sticks GOOD. I was really shocked at the effort that 185 compressor gave to get that stuff off. You never want to sit on the metal (fenders) too long with that much sand for fear of warping the panel. I had to hit an area and pull away on the primered portions for exactly that reason. I've never seen stuff stick like that. Now to be fair, I have also never blasted such fresh paint and such modern paint so there may something to that as well. Either way the general consensus is that epoxy primer is a great choice for sand blasted metal.
I used a product from a company called Southern Polyurethanes (I have no affiliation to them whatsoever) and they were very helpful. You cannot, however, use this stuff if you soda blast so be careful. I think they only deal in primer and clear so they are not a full service paint shop. I saw what my neighbor was paying for his primer and I wanted to puke thinking I would have to pay the same so I gave this a try. So far I am glad I did.
I think I paid $175 plus shipping for 2 sprayable gallons of the stuff (it needs no reducer). Three heavy or 5 light coats on your frame and it will be very difficult to remove. Though not as tough as powder coating, you can repair this easily should the need arise. The best part, however is you do not need to top-coat the stuff - even though it is called a primer. It dries to a semi-gloss so if you use it on your sheet metal you can see imperfections rather easily. It will look great on your inner fenders should you like that type of finish.
If I could use this thing better I'd show you some photos....
Good Luck
