Standard · Metallic coatings and cathodic protection
ASTM A123/A123M
Hot-dip galvanized (batch) coatings on iron and steel products.
ASTM A123/A123M is the US specification for zinc coatings applied by batch hot-dip galvanizing to fabricated and unfabricated steel: shapes, plate, pipe, bar, wire and assemblies. The current edition is A123/A123M-24.
Thickness
Table 1 gives a minimum coating grade by material category and steel thickness. The grade number is the minimum average thickness in micrometres: grade 100 means at least 100 µm. All values are minimums; the specification sets no maximum thickness. Thickness is usually measured with a magnetic gauge, with spot readings spread over each specimen of a large article.
Other checks
The inspector looks for bare spots, blisters, flux and dross inclusions and rough areas, and checks adherence. Damaged or uncoated areas are repaired to ASTM A780. Bolts, nuts and small centrifuged parts fall under ASTM A153, not A123.
4 practice items in the members area mention ASTM A123/A123M (CIP 2: 4).
Related
Try it in an exam-style question. The free readiness check shows the question style, explains every answer and gives you a dated study plan.
Take the free readiness checkSee the tracksAbout this page
This page describes the subject of ASTM A123/A123M in our own words; it does not reproduce the standard. For the full text, buy the current edition from ASTM International. Checked on 2026-10-14; errors go in the corrections log. CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.