I'm asking for advice on how to remove/treat the rusted roof joint once most has been mechanically removed.
I'm struggling with how to deal with my roof joint problem. I have an 2004, high roof, 158". The roof joints are rusted and leaking. It seems that the roof joint is just an overlapped, tac-welded joint. The paint on the outside is blistered. There are rust spots in several places on the inside at leak points. I've been reading a lot about how to treat body rust in general but not much on how to deal with rust that has permeated the overlapping roof joint. If there is rust inside the joint, I doubt that it can be stopped, slowed, yes, stopped, no. So my current plan is to use a scaler, then a scraper, then a wire brush, then sandpaper then....? The two alternatives seem to be A) using a "rust remover" based on phosphoric acid etch or B) using a "rust stabilizer" like POR15. C) Use Both. Here are my thoughts on the three approaches.
A) "Rust remover" removes the rust down to bare metal. However, two concerns: 1) will it permeate the joint and remove the rust inside the joint? 2) Will be ever be removed completely by washing? I have a problem with the idea of leaving acid inside the joint. It's electrolytic and, I suspect, will set up a kind of galvanic corrosion after I seal up the outside of the joint, thus causing the next rust outbreak. I thought of treating the joint with etch then trying to pressure wash it out. Then some kind of lengthy drying procedure... Doesn't sound like fun or give me confidence that it will work.
B) Using a rust stabilizer seems reasonable and I feel ok with the idea of leaving some of it inside the joint. However, it has high viscosity and I doubt that it will actually permeate the joint.
C) Use Both: Both doesn't seem to be an option as rust stabilizer doesn't work unless there is rust present. Etch is designed to remove rust.... Unless you remove as much rust as possible then use the stabilizer on the remaining rust. Question: what is the effect of putting stabilizer on top of bare metal? I heard it doesn't work, but can it cause problems with the top coat if it is just sitting there under the primer?
Next step: Prime. Once the rust is either removed and/or partial stabilized, it needs to be at least primed and maybe etched/primed. I'm looking at "Moeller Green Zinc Chromate Primer Outboard Paint" that's supposed to be good in the most corrosive environments, i.e. marine... Any advice on primers? Lots of primers are designed to be sandable. As such, they seem to be porous and weak. This seems to be opposite of what one wants to achieve with a primer, which is impervious and strongly bonded. I don't think that a sandal primer is a good idea. Does anyone have experience with Zinc Chromate or other Zinc primers?
After priming: Paint. Thinking a rattle can of near-color-matching Rustoleum...
After Painting: Taping / Sealing with Eternalbond tape or 3M marine sealant.
Any advice would be appreciated...