Can't decide if I should media blast the cab or not. I'm not building a trailer queen, but a daily driver. The PO said it was walnut shelled, and has been sitting in airplane primer ever since. There are a couple spots that worry me, but I feel that the more I dig, the longer and more expensive it's gonna be... when I just finished welding the firewall holes, and moving on to the underside(which has been por-15'ed already by PO) I want to paint the firewall, interior, and make sure the underside is in good shape so when i put the cab back on, I don't have to take it off ever again. And I can start wiring the truck also...

 

Only you can answer that question, what is it you see that has you worried? Bondo over a bad repair?
Not every paint job needs to be done over bare metal but the base has to be good for the paint to last. If you see something that could come back to trash a new paint job I would want to see what is under there.

 

Walnut shells don't remove rust, I would sand down any areas of concern and see if they primed over rust.

 

There's only a couple spots. I'll take some pics and post later.

 

could maybe try the fridge magnet trick to see if there is any bondo covering the bad spots? I have a '47 sedan that been in primer forever, and I plan to take it back down to bare metal cuz I want to know for sure.... but I'm OCD on such things.

 

Dustless blasting is gaining popularity in this area...it is a combination of pressure washing and ground recycled glass. Even in CA it is licensed to be done in the open, even your own driveway. Look up some of the websites and see if it will work for you. I like the idea that there is enough water to keep the surface temp fo the metal low so that there is no heat warpage.

 

I would assess the cab 'honestly' or have a second set of eyes and go from there. A couple things to consider, its NEVER as good as it appears. And it is almost always cheaper to do it right the first time.

That being said, you are looking at how much money in primer? What do you suspect is going to pop up if you do blast it? If you suspect something big, it WILL come back to bit you or the next owner and then you have to start ALL over again.

To strip and prime a cab you are looking at a couple days of work assuming everything is already disassembled. Best case scenario, you strip it, and you get fresh primer that has not been sitting and absorbing moisture or oxidizing. Plus the primer will match whatever you spray the bed and fenders with as well.

Worst case scenario, you find some rot in the usual spots and end up with a solid truck, these cabs are pretty straight forward and easy to repair. If its in a condition that you feel is going to give you a headache after blasting you would most likely already see the rotten areas

 

Here's some words of caution if you do get it media blasted:

Make sure the guy doing it doesn't use too much pressure on the doors! The shells don't have any inner support so they can bow inward or warp - permanently.
Ask me how I know.

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What about Soda blasting? I hear it is less abrasive, though I guess quite expensive..

 

Soda blast can result in similar problems as the old chemical strip (in a tank) process with material getting into crevis locations and not being able to fully get it out or neutralize it which can result in paint issues down the road.
I like ground glass in most areas and paint remover in the larger flat areas such as the large flatter areas of the doors (as mentioned by Tom) and the hood. I have media blasted my own vehicles for over 35 years with the limits listed above.

 

 

 

 

Most of these pics are corners of rockers. These areas are my only areas of concern, besides cab rear corners. There's a couple pin holes in those. I have the cab up high on a stand, so I crawled under it. Couple spots under there as well. I tried to wire wheel the areas of concern, but couldn't get in the corners

 

I sand blasted the cab on my '49 F4. I actually used silica sand. I didn't blast any of the large flat surfaces like the outside of the doors or the center of the back of the cab. It works great on the areas that you have photos of.
Mark