Dross Inclusions
Also called: dross pimples · gritty coating
Appearance
Hard, gritty particles felt and seen in or under the coating; surface looks peppered or sandy, sometimes with raised pimples.
Root cause
Zinc-iron intermetallic particles (FeZn13) from the kettle bottom stirred into the working zinc — dragging work too deep, excessive dross generation from reactive steel, or overdue dross removal.
Acceptance verdict
Generally acceptable when inclusions are small and coating thickness/integrity is maintained; gross dross that makes the coating rough enough to interfere with intended use is rejectable.
Acceptable unless the protrusions interfere with intended use or the coating below is compromised.
This is the question the standards actually answer — describe the defect, then decide: accept, repair, or reject.
Repairable?
Not an A780 repair case. Address it at the process, not with a patch — see the remedies below.
Remedy at the plant
Manage dross level (regular drossing schedule), keep work >=150 mm above the dross layer, control bath temperature, review steel reactivity mix in the kettle plan.
Remedy at design
None — this is a plant-side condition.
Clause references
- ASTM A123/A123M-24
- ISO 1461:2022
Standard designations are the property of ASTM International and ISO. This page states the acceptance outcome for this condition — it reproduces no standard text or tables. Verify against the current edition at astm.org · iso.org.