Lumps, Runs & Drainage Spikes

Also called: zinc icicles · drips · puddling

Internal corner of a galvanized steel fabrication: a thick lumpy mass of solidified zinc has pooled on the horizontal gusset plate, which has no drain hole, while the surrounding faces carry bright normal coating

Stacked galvanized gratings seen end-on, with solidified zinc hanging in rows of small icicles from the bearing bar ends — The spikes half of the same failure. Zinc that could not drain freezes where it stopped — pooling flat in a corner with no hole, or hanging off a drainage edge like this.

Appearance

Thick pooling of solidified zinc that could not drain, accumulated in corners, on gussets and inside sections; drips and runs along lower edges; spikes and icicles hanging at drain points.

Root cause

Zinc that could not drain before solidifying — withdrawal too fast, poor drainage orientation on the jig, or drain holes that are undersized, mis-placed, or simply absent. Where a design leaves an internal corner or a horizontal gusset with no hole to drain through, the zinc has nowhere to go and freezes where it sat.

Acceptance verdict

ASTM A123 & ISO 1461

Acceptable UNLESS they interfere with the intended use of the product (fit-up, assembly, handling safety). Sharp spikes are a handling hazard and are dressed regardless — ASTM names edge tears and spikes as making an article dangerous to handle, and ISO's test for sharp points is whether they can cause injury. 'Intended use' is a defined, functional term: fit-up to other parts, function, paintability — not appearance. This fit-for-intended-use test is the governing logic in both standards.

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

Slow, angled withdrawal; correct jigging angle; dress runs at finishing.

Remedy at design

This is where the defect is actually solved. Put drain holes where zinc will otherwise sit — internal corners, horizontal gussets and stiffeners, the low point of every enclosed or part-enclosed section — and size and place them correctly rather than adding a token hole. A corner with no hole in it will pool zinc every time, no matter how the galvanizer hangs it.

Clause references

ASTM A123/A123M-24
ISO 1461:2022
ISO 14713-2:2020

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.

Size vent & drain holes before the kettle — Vent & Drain Hole Calculator →