you are right, its citric acid. I guess I meant was it works the same way a dilute muriatic acid will work on metal to remove oxides and scale.As far as I know, Simple Green has citric acid in it along with a PH buffer, but I am not a chemist. I do know that I have never seen it recommended in a tech sheet for metal preparation prior to refinishing. It is a pretty decent first step to re-painting an existing finish, though.
As far as the wire brush deal and scratching back with 80, I really cannot agree with doing that. You might as well skip the ospho step. The white dusting is excess, molecules binding together, creating a film, just seems like you are removing the good it did.