Field note — finishing
Tuesday’s structural steel came out mottled and thick at the edges. Pot temperature was in band. The skim log had two blank shifts and iron in the kettle was climbing. Dross floated into the withdrawal path and rode the film.
Hot-dip galvanizing owns molten zinc chemistry and surface cleanliness, not just immersion time. Iron pickup and dross that is not skimmed become part of the coating customers reject.
Before you blame flux or steel grade
- Skim floating dross on the stated interval—signed, timed.
- Trend iron and aluminum (or other alloy) assays against the bath specification.
- Watch withdrawal path for visible dross islands after skim.
Rule
No production dip after a missed skim window without a signed chemistry check. Raising pot temperature to “fix dullness” without skimming buys thicker scrap.