I think if there are pits that need to be cleaned out it no longer qualifies as "Surface" rust...
Vinegar (Acetic acid) is not the same as Ospho (Phosphoric acid)
Acetic acid, the active ingredient in vinegar, will form iron acetate on contact with steel. Can anyone show any good info on the effectiveness of iron acetate as a passivation layer, or on its effect on coating adhesion?
In contrast, the properties of iron phosphate conversion treatments and zinc phosphate passivation layers are well known, and actually compatible with epoxy. (edited/paraphrased from a post by crashtech on a painters forum)
Ospho or no, it still needs to be properly neutralized for the premium grade epoxies to work properly.
