Seal rust pits BEFORE primer.

Yes ospho will work BUT, make sure you neutralize it . Wash it off very very good, soap an water.

When you say neutralize it do you mean wash the metal off after you have painted the ospho on? If so how long should you wait after the ospho has gone on.

I ask this because I am cleaning up my floor boards and have wire brushed down to bare metal on 2/3's of the entire floor. Even though I am not finished I painted the area I had done with ospho (1 layer) to prevent flash rusting until I can finish this weekend. I did this about a week ago and the area now looks strange: Some clean bare metal still looks like shiny bare metal, there are some dried up black bubbled looking areas, some white hazy looking areas, and then some areas that actually look rusted again.

I intend to go over the entire floor with a couple layers of Por-15 when I am done cleaning the rust up. Should I re-wire brush the rusted looking areas and re-ospho the rusted looking areas again before painting. I want to make sure I do it right the first time. Any input would be GREATLY appreciated.