Ash Inclusions
Also called: skimming marks · ash staining
Appearance
Dull grey-white deposits or streaks on the surface; loosely adherent ash sitting on or lightly bonded into the top of the coating.
Root cause
Zinc oxide/ash film on the bath surface pulled onto the work during withdrawal — inadequate skimming ahead of the withdrawal path or too-slow withdrawal.
Acceptance verdict
A123 treats this case by name: zinc skimmings — oxide and chloride particulates off the bath surface — clinging to the work are not cause for rejection, because the coating beneath them is intact and protects as intended. They brush off, weather off in rain, or are ground off by the galvanizer, provided the grinding does not take the coating below its minimum thickness. Where ash sat between steel and zinc and prevented the coating forming, that is an uncoated area and is judged under the renovation limits instead.
A removal duty, not a defect listing: flux residues and zinc ash shall be removed where they can affect the article's intended use or its corrosion resistance — with an access exception for surfaces that cannot be reached, such as inside hollow sections. Deposit on intact coating that affects neither is an appearance matter; ash that prevented coating is an uncoated area under the renovation limits.
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
Skim immediately before withdrawal, correct withdrawal speed, keep the withdrawal window clear.
Remedy at design
None.
Clause references
- ISO 1461:2022
- ASTM A123/A123M-24
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.