My Cracks Are Showing!

I searched the archives, but couldn’t find an answer. I restored my N ford last year, but had to store her outside before I could do my final touch-up on the paint. A lot of the seams where the castings go together, plus most of the bolts and nuts have developed a pretty good rust film. I need to figure a way to remove (or seal) the rust so I can apply paint, but I REALLY don’t want to have to blast, mask and repaint just for one bolt head or 1/16 seam. I’m planning on doing the touch-up with small paint brush.

Will phosphoric acid work? Will it destroy my existing (PPG) paint? What about POR-15? I thought about going in with a Dremel and a small wire brush, but is there a better way? If I don't have to take it to bare metal, prep, prime, and spray I'd be ecstatic!

Thanks for the help!

Roger

I have used phosphoric acid treatment as a clean metal pretreatment prior to painting but not as a rust "treatment" step. Not that it wouldn’t work mind you...just that I have used it only on surfaces that might contain microscopic rust that you cannot see. An example would be "bright metal" sandblasted surfaces or paint stripped surfaces that have no visible rust. See my post below on the subject. This type of treatment involves a part 1 apply, scrub, wash, part 2 apply, scrub, wash work sequence if you follow the manufacturer’s recommendations. It is time consuming and messy...probably only warranted on the highest quality (and $$$) jobs. It is NOT a process that I would look forward to for individual bolt heads or nuts or seams. The materials are all the consistency of water and will run down across your adjacent painted surfaces. I doubt that would destroy anything but some staining is a possibility.

As far as actual rust "treatments" go, I have tried two products...Rust-Mort by SEM Products and Extend by Loctite/Permatex. The Rust-Mort is a phosphoric acid-based product that is applied as one step with three or four coats. The Extend is some type of polymer-based product that is applied as one step in two coats. My application here is the underside of a severely rusted dump truck body. I will not be blasting to bright metal but I want to try and limit further deterioration of the steel. Last fall I applied both the above products to a small area after I removed the loose rust by high pressure water blast. The test area was severely pitted. I was not impressed with the Rust-Mort. It is the consistency of water and will run down any inclined surface. The best I can say for it is that it might do well in seeping into little crevices and cracks that otherwise would not get treated. On the other hand, the Extend is a much heavier consistency...more like actual paint. It turns a jet black in a few minutes after contact with rust and provides a hard coating. It goes on easily and doesn’t run. Of course you top-coat it to match your surrounding paint. Even though the SEM people assured me that Rust-Mort was ideal for my application, I have decided against it and will use Extend when I get back to the project this spring or summer.

I have no experience at all with POR-15 but from what I have seen in photos it appears to be quite similar to Extend. I think the artist brush approach will work fine. Hope the above has been helpful food for thought.

Rod