Popping refers to countless tiny holes forming in a paint film after baking.
Q1:
Holes that form when moisture evaporates and escapes from the paint film.
A1:
Reduce excessive film thickness and rapid temperature increases.
Q2:
Holes that form when air bubbles entrapped in cracks in the plating of galvanized sheet steel expand and
escape.
A2:
Care should be taken when changing the sheet steel type. (plating, plating mass per unit area, etc.).