Hi everyone, Let me start off by saying that I am not a painter or a pro body guy but I am working towards getting my cab prepared for primer and paint. I was looking for some guidance on how to remove the rust still slightly pitted in the roof of my cab after a 150 grit then a 220 grit sanding. I do not have access to a sand blaster so I didn't know if dropping down to a 60 grit to really cut in was advisable. Looking of suggestions.

 

Scotchbrite pad and then use a neutralizer.......

 

I would personally use Picklex 20 rubbed in as per instructions and then let it sit 24 hours before priming. Relatively expensive but then I have used my 32 oz. bottle for 9 years now.

 

Check out this post https://www.ford-trucks.com/forums/1...st-repair.html
My post is #7, on the roof I would use the Eastwood disc and strip it down to bare metal as there will be rust under the paint that is left on.
I would then hit the whole bare metal roof with the acid and Scotchbrite pad and work it in, it will turn the rust black.
I let it sit till dry, over night or more as needed, then use a sponge and clean water to wipe the panel down to remove any thick areas. Wipe and / or air gun blow it dry.
Depending how deep the rust pits are I may hit them with a thin coat of filler, sand & prim or a few heavy coats of primer.

The whole roof of my truck was like that after I took all the filler off. I pulled the dents and used the acid as above.
I also used it in the doors and moved the doors around to work it in to the seams between door frames & skins to fight rust. In the doors I did not use water after as it will not be seen of finished like the outside body panels.
Dave ----

 

I'm working on this at this moment. I have been remarkably successful doing this:

Use a paint/rust stripper disk from Lowes, Home Depot, etc. They cost about $10 and attach to a 4 1/2" angle grinder. They do not harm the metal but can get those little pits of rust.

When the metal is as clean as you can get mechanically, I use acid. Ospho is my favorite and it works great and doesn't cost much. I use a spray bottle. Wear a respirator or spray from up wind. Even a dust mask would help for this. Let the acid sit for 24 hours. It will turn black and leave a slight crust that can be brushed off with 80 grit or a green scotch brite pad.

The acid will be inert after the 24 hours, but i use 91% isopropyl (rubbing alcohol), to thoroughly clean the metal again. Now you're ready for primer. I prefer epoxy on body panels, and I have used etch primer on the frame. The epoxy can be sprayed directly over the metal and here's the best part, you're done. The metal is protected. Now, with a little scuffing with sandpaper, you can use body filler directly over the epoxy and when the body filler cures, spray epoxy over that to seal it. The metal is never exposed again, so flash rust is no longer a concern, and the acid, (phosphoric, NOT muriatic), will leave a coating a iron phosphate on the surface shielding for rust. Basically, the bare metal even when exposed, will not rust for a few weeks to a few months.

You'll need a filler primer on top of the epoxy and that can be sanded down, usually with 600 grit, and sprayed with your topcoat of choice. The filler primer, or urethane primer, will fill in the small dents and pits caused by the rust. It need the epoxy to bond to the metal though. You cannot skip the epoxy primer to save money. It will not adhere. Also, make sure you wait the 24 hours after the acid to shoot the epoxy or it will not adhere.

The acid can also be used inside panels and flows like water, to reach everything. I love it and it works great if you follow the directions.

I have a YouTube channel, and in the most recent parts, I demonstrate some of this.
www.youtube.com/channel/UCIqAoRwpl-fDBKz-Op_DKTQ

 

Thanks for the replies and suggestions.
I think I'll go with the Ospho. I was using evaporust and while it did work to some degree, I was not happy with the penetration because I can still see the rust in the tiny pits. Thanks again. I'll let you all know how it goes.