ASTM A153
Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware
Specifies hot-dip zinc coating on centrifuged or otherwise handled iron and steel hardware.
What ASTM A153 specifies
ASTM A153/A153M covers batch hot-dip galvanizing of iron and steel hardware. Class A applies to castings; Classes B-1 through B-3 divide rolled, pressed, and forged articles by thickness and length; Classes C and D cover larger and smaller fasteners and similar articles. Minimum average thickness ranges from 43 µm for Class D to 86 µm for Class A and B-1, with lower individual-specimen limits. The selected class follows part geometry rather than an arbitrary corrosion tier. Buyers should state class, thread accommodation, appearance, spinning requirements, masking, and whether ASTM F2329 is required for threaded fasteners.
ASTM A153 types and classes
Every designation the document defines, with the thickness it requires and the tests it imposes.
| Designation | Meaning | Thickness | Coating weight | Requirement / test |
|---|---|---|---|---|
Class A | Malleable iron and steel castings. | ≥ 86 µm ≥ 3.4 mil | 610 g/m² minimum average; 550 g/m² individual. | Average and individual thickness or mass. |
Class B-1 | At least 15.88 mm thick and over 381 mm long. | ≥ 86 µm ≥ 3.4 mil | 610 g/m² minimum average; 550 g/m² individual. | Average and individual thickness or mass. |
Class B-2 | Under 15.88 mm thick and over 381 mm long. | ≥ 66 µm ≥ 2.6 mil | 458 g/m² minimum average; 381 g/m² individual. | Average and individual thickness or mass. |
Class B-3 | Any thickness and 381 mm or less long. | ≥ 56 µm ≥ 2.2 mil | 397 g/m² minimum average; 336 g/m² individual. | Average and individual thickness or mass. |
Class C | Fasteners over 9.52 mm diameter and washers at least 4.76 mm thick. | ≥ 53 µm ≥ 2.1 mil | 381 g/m² minimum average; 305 g/m² individual. | Average and individual thickness or mass. |
Class D | Fasteners 9.52 mm diameter and under, rivets, nails, and washers under 4.76 mm thick. | ≥ 43 µm ≥ 1.7 mil | 305 g/m² minimum average; 259 g/m² individual. | Average and individual thickness or mass. |
Tests and the drawing call-out
Tests the document imposes
- Average and individual coating thickness or mass
- Visual finish and freedom from uncoated areas
- Adherence
- Embrittlement where applicable
- Thread fit
How to cite it
Drawing call-out
HOT-DIP GALVANIZE HARDWARE PER ASTM A153/A153M, CLASS <A|B-1|B-2|B-3|C|D>, <THREAD REQUIREMENTS>Angle brackets mark the choices the drawing must make; every finish page shows a completed example.
Finishes specified to ASTM A153
ASTM A153 — frequently asked
What determines the A153 class?
Part form, dimensions, and hardware category determine it. The classes are not freely selected corrosion levels.
How thick is Class D?
Class D requires 43 µm minimum average and 36 µm on any individual specimen. It covers small fasteners and similar hardware.
Should bolts use ASTM A153 or F2329?
ASTM F2329 is specifically structured for threaded fasteners and is often preferred. Follow the drawing and applicable fastener product standard.
ASTM A153 is copyrighted by ASTM International. This page explains the document so a drawing can be read; it does not reproduce the standard. Purchase the current edition from the publisher. Official source ↗