Internal cavity rust treatment, Would/do you use Ospho? Options

[bbrock]

This question is specifically for those enclosed cavities that do not get opened during a full rustoration. On my car, there aren't many (inner cavities of roof pillars, roll bar, windshield frame, trunk cross member, and inside driver's suspension console). I bought a bunch of tubing to modify a garden pump sprayer so I could spray Ospho/Jasco inside those cavities. My thinking is that it would seep into seams where there is ALWAYS rust even in parts in good condition, and convert whatever rust it contacts. This would be followed by treating with Eastwood Internal Frame Coating, and finally, 3M Cavity Wax Plus. So two questions about the Ospho treatment:

1. Would you do it? It makes sense in my head, but it is spraying acid inside structural components.

2. If you did, would you follow with a water spray to neutralize the acid? My understanding is that the product forms a protective coating that can be left indefinitely, but it needs to be neutralized before it can be painted. For internals, I wonder if I'd get better long-term protection by just spraying Ospho and leaving it alone.

Thoughts?

[76-914]

I don't think your supposed to get that stuff on good metal, are you? (IMG:style_emoticons/default/confused24.gif) Wouldn't the frame coating stop the rust that is already present? (IMG:style_emoticons/default/beerchug.gif)

[bbrock]

I don't think your supposed to get that stuff on good metal, are you? (IMG:style_emoticons/default/confused24.gif) Wouldn't the frame coating stop the rust that is already present? (IMG:style_emoticons/default/beerchug.gif)

Ospho and similar is designed as a metal prep for metal regardless of whether it is rusted. From what I can tell, it etches the metal to provide "tooth" for painting, converts rust to some benign compound that I can't remember, and leaves a protective phosphorous coating to help protect the metal. The data sheet for the PPG epoxy primer I'm using actually says "Chemical treatment or the use of a conversion coang will enhance the adhesion and performance properes of the finished system."


I've had a hard time getting details on how the internal frame coating works. IIRC, they have it listed as an "encapsulator" which suggests it doesn't convert rust by seals it so no oxygen can get to it. That should stop further corrosion IF you get complete coverage. I was thinking of the pre-treatment with Ospho as more of a belts and suspenders approach. First, convert as much rust as I can, then encapsulate. I've also considered spraying epoxy primer instead of internal frame coat using the same modded pump sprayer.

rjames, that is the exact same thought process I'm going through. Water in the internals seems bad, but I wonder if not doing it will interfere with adhesion of coatings. Also wondered if going over all the seems with a heat gun to steam out the water after spraying would be sufficient to dry things quickly.

Ultimately, I think cavity wax is the real hero in the arsenal I plan to use against rust. I've used it before and have been very impressed. Almost 30 years ago, I did a piss poor patch on my pass jack point and sprayed in cavity wax using a homemade application wand. When I opened it up to replace the long on this project, all the places with wax looked pristine even on bare metal, while the rest of the metal had corroded to dust. Now they have wands and have reformulated the product so you get much better coverage. No affiliation, it's just good stuff:


https://www.youtube.com/watch?v=OfisO8h8vYY