Unpainted Ospho-Treated Metal

cmfisher4

Promoted Users
I'm using Ospho, as necessary, on some rusty spots and following SPI's recommendations prior to putting down epoxy. No issues so far. But, I have some internal, mostly inaccessible locations, inside a B-post for example, where the vertical portions of the steel are rusty, but not horrible (no pits). I had a brilliant idea, since I can't access those areas for paint, it may be worth it to use a long brush to get Ospho on it to convert over the rust and leave it as-is, without paint, to serve as a protective layer before I seal it back up with my new panels and repair patches.
If I learned one thing during the restoration of my Spitfire, it's that my brilliant ideas aren't always so brilliant. So, I was curious what you guys thought. Doing this would be "off-label" as I don't see any instructions by Ospho that supports doing this without following it up with paint.

Thanks,
Chris
 
I do this all the time, except I use a metal prep that has zinc phosphate in it as well. When left on the metal, it will not harm anything. Eventually the metal will start to rust again with time and humidity.
 
surface rust on interior surfaces will never rust thru unless the is enough dirt to hold moisture.
 
I'm using Ospho, as necessary, on some rusty spots and following SPI's recommendations prior to putting down epoxy. No issues so far. But, I have some internal, mostly inaccessible locations, inside a B-post for example, where the vertical portions of the steel are rusty, but not horrible (no pits). I had a brilliant idea, since I can't access those areas for paint, it may be worth it to use a long brush to get Ospho on it to convert over the rust and leave it as-is, without paint, to serve as a protective layer before I seal it back up with my new panels and repair patches.
If I learned one thing during the restoration of my Spitfire, it's that my brilliant ideas aren't always so brilliant. So, I was curious what you guys thought. Doing this would be "off-label" as I don't see any instructions by Ospho that supports doing this without following it up with paint.

Thanks,
Chris
2 years ago I treated a rusty piece of 10 inch iron pipe with 2 coats of Ospho after hand wire brushing the biggest loose rust scale off. It is 100% out in the weather and no new red rust has started on it except where it has been scratched by other scrap in the pile. I think it will be just fine in your B-post.
 
Wow, thanks for the quick replies! I don't expect this to be a permanent fix, just trying to prolong a bit. I don't expect a rust-through problem, but I figured this would be a way to arrest it (we used it on the submarine in the bilge all the time).

My concern for putting epoxy down is that while I can get a paintbrush in there (at least most of the way), I would not be able to adequately prep the surface for epoxy (neutralize the Ospho) adequately and just be wasting my time and good paint.

Interesting experimental results, 1A Rock. Good to know.
 
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