I've never understood why more people don't use zinc phosphate when it has numerous benefits over phosphoric acid.
For one, it removes rust better than acid treatments, it doesn't have to be neutralized, it leaves a nice gray zinc coating on bare metal surfaces giving protection against corrosion AFTER application (phosphoric acid gives no protection after application), application is far less messy (it's sprayed on),and is compatible with virtually all paint systems (phosphoric acid is not, ie SPI does not recommend their Epoxy over acid-treated surfaces).
I treat all my panels with zinc phosphate once I've got them to bare metal to protect against flash rust as well as remove any corrosion I couldn't remove mechanically. It also leaves the panel looking brand new.
There may be some other products out there, but I use a particular one, made right here in good ol Iowa called Phix by a company called PPC