Originally Posted by
Ol Danl
I think maybe you have to paint over the Ospho, or neutralize it, or the acid will promote further rust. I've gone ahead and primered the frame section and battery tray, since they are both thick steel in the first place. Waiting for warmer weather to paint it so I can put it back together. Really want to know how to do this for the steel rims on a bike project, though.
Yes, you must paint over Ospho, and any brand of rust converter. They do not provide [I]any[I] protection to the metal, only to convert existing iron oxide (rust) to iron phosphate or magnetite, respectively.
I work on ships and we have, as you might imagine, quite a lot of rust/paint problems, so I'm always interested in different approaches and results.
In my experience Ospho works very well and rust converter is more situation dependent. Neither Oshpo or Rust Converter (I would recommend Corroseal brand, widely used on ships) will work if the scale has not been removed.
Ospho is not as temperature dependent, but does work much faster when exposed to sunlight.
As for steel rims, I've been contemplating this as well for some old 28" Westwoods. I think I'm going to go for the Ospho. It will produce a sort of white film when dry where it has converted rust. You can wipe this away with some solvent and call it good. That is what I'm going to do.