not just manufacturing residue, lots of people want to use a brass nut or something in their column, leibig, or parrot, but can't because the lead will leach into the "product" so passivation's the only way to put it into the vapor path.
Distillers are fastidious about not using any parts with lead.
(note: past life-time, now i'm vaping on MMJ, so don't drink anymore)
thanks for the info about Ph level