[markwilltoo]

The only way to prevent rust from eventually bubbling through the paint some years later is to use quality automotive grade epoxy primer under your paint. It's expensive, but will not allow any moisture pass through the finish. Lacquer primer begins absorbing moisture from the air as soon as it dries and will eventually rust through the primer, depending on ambient humidity if not top coated

Phosphoric acid goes inert once dry and will not provide long term protection if exposed to high humidity.