What does bonderized mean in the T-Top 4 in. Bonderized Steel Exhaust Vent Pipe Flashing?

Bonderized is an additional coating, with an anticorrosive phosphate solution applied over galvanized steel.

Bonderized is an additional coating, with an anticorrosive phosphate solution applied over galvanized steel. This finish is preferred when the intention is to paint the product and allows for better paint adherence.