Need some primer/prep advice.....

Well I need a little advice on some issues on my sedan. I stripped the rotten wood frame work from my front doors, and am ready to start fabbing a new steel frame work.

The doors are stripped to a bare skin, and are in real solid shape, no rust-outs/bubbles etc at all, just surface rust on the inner skin where the old rotten wood frame was.

I am gonna need to have the inner skins blasted to get the surface rust all gone before I build the new door frame. Its really the only way to get it clean, as many areas are too confined around the window frame to grind or sand it at all. It will easily be 1-2 months before the car sees paint, so it will be bare(but indoors) for a while before I can prime/and paint it.

My finish plans are to epoxy prime, then single-stage urethane the inner & outer door skins. My question(finally)is this:

I know that the doors will flash rust some before I can prime/paint them. If I ospho or dupont metal prep them after the fab work is done, will epoxy primer stick properly to the etched surface?

I did a search, but didn't get a great answer. Another reason I wanted to ospho(or whatever is the best) the inner doors is to kill the rust completely so it doesn't haunt me years later. There is very minor, shallow pitting on the door skin under where the old wood sat, and I really want to keep it from growing worse. But I don't want adhesion problems with the epoxy primer later.

I am definitely NOT a paint/body guy by any stretch, so I would really appreciate any advice. I'm not looking for the easiest, cheapest fix, but instead the best most permanent way to make this right would be.

Thanks in advance, sorry for the long post
Dan

P.S. Heres an old pic when I was building the body's subframe. it shows the inner door skin to give you and idea of why it needs blasted

 

Yeah. ospho or however you spell it is the way to go. It won't 100% stop light surface rust from happening, but it'll damn sure cut it back off before you prime. We usually rinse pretty good with water after we use it, never had a problem with anything sticking afterwards, wether we were shooting epoxy, urethane, whatever. We tend to wipe EVERYTHING down with ospho...it does a killer job taking that dark colored nasty shit off DOM tubing.

 

You're on the right track. Epoxy primer on a clean etched surface is about as good as it gets. Any professional grade prep like the dupont you mention will do. I usuall try to rinse with at least distilled water. Don't be too reluctant to preserve your bare metal with WD40 or similar as you work. A little brake cleaner drys it right out when youre ready for etch/prime. If your surfaces are nice you can paint right over the epoxy with out sanding. There's usually a 3 day window for that so an overnight epoxy dry is a good thing. You can also use primer/surfacer right over if sanding is desired in certain areas but not the entire surface. I like POR15 also. On etched metal it's pretty damn permanent. Perfect for places you never see.

 

Hey guys thanks for the quick, helpful replies, I appreciate! I am glad to hear that should be ok. My biggest concerns with ospho or dupont 5717s was that they said to do a test panel for use under epoxy finishes first. And I sure didn't want to get to priming it and have crazy adhesion problems going on.

I have used ospho before and had good results, but never under epoxy primer, and the warnings scared me a bit.

 

Your on the right path, but I would honestly prime the doors even while they sit. There's no reason you can't prime parts or panels individually, the key is when you paint you want to spray the whole car at once to insure good color match and tone. I spray Valspar myself, but have used some dupont paint, no primers. I cover all my projects piece by piece with "DTM" primer, that is Direct To Metal and it's great. If you do however choose to wait and prime all at once, just wipe it good with some prep sol or somethin of that nature and the rust won't give you any problems.