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.
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.
ASTM F2329
The standard specification that covers the requirements for hot-dip zinc coating applied to carbon steel and alloy steel bolts, screws, washers, nuts, and special threaded fasteners applied by the hot-dip coating process. Nails and rivets are not included in F2329. It is intended to be applicable to fasteners that are centrifuged or otherwise handled to remove excess zinc.
ASTM F2329 vs. ASTM A153
A153 covers galvanizing on many products including fasteners, while F2329 is specific to threaded fasteners, nuts and washers. The two specifications have virtually identical coating thickness requirements. Also, A153 and F2329 have different sampling requirements; F2329 requires more samples per lot than A153. Portland Bolt can meet the requirements for both F2329 and A153 Class C. Portland Bolt performs hot dip galvanizing of threaded fasteners within our 137,0000 square foot manufacturing facility. Contact us if you have a need for hot-dip galvanized fasteners or with any technical questions regarding hot-dip galvanizing. One of our experienced sales reps will be happy to answer any of your questions.
I want to know how thickness requirement zinc coating in 25 mm dia of steel plain bar
@M- The zinc thickness will depend on the process used. Long bar will be galvanized per A123, whereas shorter lengths or bar with threads will be processes per A153/F2329. The two standards have different minimum zinc thickness requirements.
What is the typical hot dipped galvanizing spec for typical washers? A123 seems to be the logical choice, but it looks like A153 could be used too.
@Steve- A123 is for unthreaded articles that are not centrifuged, so more like beams and structural shapes. For small articles that need to be spun (like washers), you can use either A153 or F2329. F2329 is the standard referenced by all of the ASTM fastener standards (like F436, F844). A153 would be more appropriate for nonstandards, although both galvanizing standards are about the same.