I've never used Ospho, or products like it. I have some just never tried it. I assume you don't clean it off after using it, just let it dry and paint over top? I was always concerned it would leave an acidic residue that would affect paint.
I've started to clean my frame, using a chipping hammer to remove loose stuff then a wire wheel to clean it further. I just painted it with rust paint after that. It turns out alright but doing the inside of the frame is a bear.

 

If you put the Ospho on thick, it will leave a sticky residue that will take several days or a week to dry. When I tackle a heavily rusted project, I'll knock off the loose rust with whatever means are necessary, then I brush on some Ospho and leave it for a few days to dry. I'll then go back and scuff the entire part, ospho'd areas and all, with emery cloth or wet/dry in the appropriate grit. The next application of Ospho I put on with a spray bottle and try to put on as little as is necessary. After it had dried again, before I spray any paint, I'll wipe the project down with a good degreaser.

 

I have a question for you weymouth. I see that you had some rust in your drivers door on the bottom. Did you fix the door or did you replace the door? From the pictures it looks like you might of replaced both doors because I see different mirrors on the doors from the before and after pictures. If you did fix the doors got any pictures? Im going to fix my doors rather than replace them. Thanks Fred

 

rYou're correct, they're from a '92 F150 4x2 from my brother in law (look at this thread for a little back ground on the brother in law https://www.ford-trucks.com/forums/s...d.php?t=287689)
His truck finally proved to be too unreliable after 411,782 miles, so he offered it to me for parts(?) for free. Basically, he was just looking for someone else to get rid of it for him.

Since neither of my doors had bottoms (I mean only the outer skin was left) and both his doors were in much better shape, (and I wanted to switch to newer style mirrors) I took him up on the deal. I still had to patch the new passenger door in a couple of places near the bottom. If I had an opportunity to go back and do it over, I'd just cut the sections I needed from the newer doors and weld them onto my original doors. Everything about the original 89 doors is better than the 92's. The 89 doors are stonger, have better latches, better inside handle mechanisms, beefier regulators and better window gaskets. I had already cut sections from the skin of the old doors for patches elsewhere on my truck, so re-using them was out of the question. With the exception of the glass and window tracks, all the hardware and locks from the 89 doors is now inside the 92 doors.

I also took from the 92, the rims (which were already on my truck in the before pictures), the seat back w/ the head rests, the stereo (but it's going to be used elsewhere), the mirrors, and a few interior odd and ends. The driver side mirror had been replaced with an all black one, so rather than try to make it look like chrome, or the passenger one (which was chrome) look black, I scuffed and painted them both the same color as the truck.

I should also add that I replaced both fenders with a near perfect set of 87's, from a junk yard ($90 for the pair). I also took off all the emblems (F150, 4X4 etc...) and welded the holes.

 

Thanks for the info weymouth. I'll have to order my patch panels for my doors. Good thing was that my truck was undercoated when it was brand new back in 82 so the rust isn't as bad as it could be. I can see it inside the door when I took the door panel off. Fred

 

Hey weymouth, I got another question im hoping you can help me out with. I just fixed my core support on my 82 F100. The problem is I don't know if the brackets that are riveted to the frame are good or not. From the rust over the years I don't know if the hole in that bracket that the bolt goes through is the correct size or not. Im sure you know the bracket im talking about, one on each side has the body mounts on. The holes on mine that the bolt goes through are 2 1/2 inches in diameter. I don't think they are supposed to be that big. Do you remember how big yours where when you did your fix? Thanks Fred