Hot dip galvanized steel ASTM A123M
Table of contents
ASTM A123/A123M
ASTM A123/A123M Requirements
What is the difference between ASTM A123 and A153?
ASTM A123/A123M
The specification ASTM A123/A123M Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products, covers individual steel pieces as well as assemblies of various classes of material. The six material categories covered in ASTM A123/A123M include structural shapes, strip and bar, plate, pipe and tubing, wire, and reinforcing bar. A fabrication can have more than one material category such as a frame assembly. Any combination of these products can be assembled into a single fabrication and then hot-dip galvanized.
ASTM A123/A123M Requirements
Coating Thickness / Weight dependent upon material category and steel thickness
Finish continuous, smooth, uniform
Appearance free from uncoated areas, blisters, flux deposits and gross dross inclusions as well as having no heavy zinc deposits that interfere with intended use
Adherence the entire coating should have a strong adherence throughout the service life of galvanized steel
The hot-dip galvanized coating is intended for products fabricated into their final shape that will be exposed to corrosive environmental conditions. Once a product has been hot-dip galvanized, any further fabrication, which rarely occurs, may have negative effects on the corrosion protection of the coating. The coating grade is defined as the required thickness of the coating and is given in microns. All coating thickness requirements in specification ASTM A123/A123M, (Tables 1 and 2), are minimums; there are no maximum coating thickness requirements in the specification.
| Table 1: Minimum Average Coating Thickness Grade by Material Category |
| All Specimens Tested Steel Thickness Range (Measured) in. [mm] |
| Material Category |
<1/16 [<1.6] |
>1/16 to <1/8 [>1.6 to <3.2] |
>1/8 to 3/16 [>3.2 to < 4.8]
|
>3/16 to <1/4 [>4.8 to <6.4] |
>1/4 to <5/8 [>6.4 to <16.0] |
>5/8 [>16.0] |
| Structural Shapes |
45 |
65 |
75 |
75 |
100 |
100 |
| Strip and Bar |
45 |
65 |
75 |
75 |
75 |
100 |
| Plate |
45 |
65 |
75 |
75 |
75 |
100 |
| Pipe & Tubing |
45 |
45 |
75 |
75 |
75 |
75 |
| Wire |
35 |
50 |
60 |
65 |
80 |
80 |
| Reinforcing Bar |
-- |
-- |
-- |
-- |
100 |
100 |
| Table 2: Coating Thickness GradeA |
| Coating Grade |
mils |
oz/ft2 |
µm |
g/m2 |
| 35 |
1.4 |
.8 |
35 |
245 |
| 45 |
1.8 |
1.0 |
45 |
320 |
| 50 |
2.0 |
1.2 |
50 |
355 |
| 55 |
2.2 |
1.3 |
55 |
390 |
| 60 |
2.4 |
1.4 |
60 |
425 |
| 65 |
2.6 |
1.5 |
65 |
460 |
| 75 |
3.0 |
1.7 |
75 |
530 |
| 80 |
3.1 |
1.9 |
80 |
656 |
| 85 |
3.3 |
2.0 |
85 |
600 |
| 100 |
3.9 |
2.3 |
100 |
705 |
|
A: The values in micrometers µm are based on Coating Grade. The other values are based on conversions using the following formulas: mils=µm x 0.0.937; oz/ft2= µm x 0.02316; g/m2 = µm x 7.067
|
What is the difference between ASTM A123 and A153?
ASTM A123 does not cover threaded bolts and fasteners. ASTM A153 and F2329 are the ASTM specifications that cover the requirements for hot-dip zinc coating of fasteners.
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ASTM A123
This specification covers the requirements for hot-dip galvanizing on iron and steel products made from rolled pressed and forged shapes, castings, plates, bars, and strips. It does not cover threaded fasteners that are centrifuged or otherwise handled to remove excess zinc.
ASTM A153
This ASTM specification covers zinc coatings applied by the hot-dip process on iron and steel hardware. This specification is intended to be applied to hardware items that are centrifuged or otherwise handled to remove excess zinc. A153 is applicable to steel hardware items of Classes A, B, C, and D.
Class A – Castings – Malleable Iron, Steel
Class B – Rolled, pressed, and forged articles
Class C – Fasteners over 3/8” diameter and washers 3/16” and ¼” thick
Class D – Fasteners 3/8” diameter and smaller, rivets, nails and washers under 3/16” thick
Since threaded fasteners are spun at high speeds in a centrifuge to remove excess zinc from the threads, they would fall under the A153 class C specification.
