What's the Best Way to Prep Unknown Condition Steel?

[RichardR]

Hi,
I pan on starting body work soon on my 71 Scamp and I have questions about prepping the metal. I've never done this before so it is a learning experience. My C pillars are solid but rusty due to being an old vinyl top. I will do my best to remove rust from this area and the roof. I'm worried that rust may still lurk in pitted areas. What's the best form of metal prep that will work on the steel and convert or remove rust?

I know there are different options, just looking for people's opinion. Does phosphoric acid work well?

Can I epoxy prime over POR15 metal prep if I use that?

 

[gzig5]

I've been using Ospho lately with pretty good results. I think it's a form of phosphoric acid. It's cheap, available locally, and easy to use. Doesn't hold on vertical surfaces so well but I'm going to try soaking a blue paper towel in it and wrapping it around and see how that works. When it is dry you can prime and paint over it. Eastwood has a bunch of options but they start to get expensive and the shipping isn't cheap unless you get a big order in.

Not positive but I think you can use epoxy primer over POR15 if you rough it up first.

 

[MoparMike1974]

I have been using ospho for years. If the metal is pitted bad you might have to spot blast the bad areas to get it clean.
I use steel wool with the ospho and scrub the metal with it. After scrubbing wipe it dry. It will dry after an hour or so and will stay protected from flash rusting for a very long time as long as it doesnt get wet. When your ready to prime it should be sanded down to remove the coating and rough up the metal for adhesion.

 

[RichardR]

Cool. I think I know where to get ospho locally. What's a decent primer company that isn't horrible for shipping? I'm located in Ontario Canada btw.