Wet-Storage Stain (White Rust)
Also called: white rust · storage stain
Appearance
White to grey powdery deposit, from light film to bulky build-up, typically where surfaces were stacked in contact.
Root cause
Moisture trapped between closely packed, freshly galvanized surfaces without air circulation — zinc corrodes rapidly before its protective patina forms. Newly galvanized zinc is most vulnerable.
Acceptance verdict
ISO 1461 answers the acceptance question in one sentence: the development of wet storage stain shall not be a cause for rejection, provided the coating thickness remains above the specified minimum. That is the whole test — remove the deposit, measure what is left, and the article stands or falls on thickness, not on how alarming the white bloom looked. The working grading galvanizers apply on top of that is guidance practice: light and medium stain is removed and the work accepted where thickness holds; heavy stain with real zinc loss, or red rust showing through, means the protection is gone locally and the article is re-galvanized.
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
Passivate/quench per practice, ship dry, never wrap or stack wet work tightly.
Remedy at design
Store with spacers at an angle for drainage and airflow; keep off wet ground; ventilate covered transport.
Clause references
- ISO 1461:2022
- ISO 14713-2:2020
- GA UK wet storage stain guidance
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.