ASTM F2329

ASTM F2329 – Hot-Dip Galvanized Fasteners

ASTM F2329 specifies the requirements for hot-dip zinc coatings on carbon steel and alloy steel fasteners such as bolts, nuts, washers, screws, and other threaded parts. The process involves applying the zinc coating by hot-dip galvanizing, followed by centrifuging or other methods to remove excess zinc and ensure a clean finish.

This standard, first introduced in 2005, was created specifically for fasteners and is gradually replacing ASTM A153 as individual fastener standards are revised. ASTM F2329 ensures consistent corrosion protection and coating quality for threaded fasteners.

For comparison, ASTM A123 is another hot-dip galvanizing specification, but it applies to structural steel shapes, plates, bars, strips, castings, and forgings rather than fasteners.

Dimension	Minimum Coating Thickness
Dimension	Avg. of All Specimens (Production Lot)	Avg. of All Specimens (Batch Lot)	Individual Specimen
Bolts/Nuts over 3/8” diameter	0.0020 in.	0.0017 in.	0.0017 in.
Washers 3/16" – 1/4" thick	0.0020 in.	0.0017 in.	0.0017 in.
Bolts/Nuts 3/8” diameter & under	0.0017 in.	0.0015 in.	0.0015 in.
Washers under 3/16" thick	0.0017 in.	0.0015 in.	0.0015 in.

Effect of Temperature on Mechanical Properties

Unless otherwise specified, testing for mechanical properties is not required if the galvanizing process is performed at a temperature lower than the stress-relief or tempering temperature of the fasteners.

Threaded fasteners manufactured from carbon or alloy steel and heat-treated to a specified hardness of 40 HRC or above, as well as case-hardened fasteners, shall not be hot-dip galvanized.

Effect of Hydrogen on Mechanical Properties

For fasteners with a specified minimum hardness of 33 HRC or higher, there is a potential risk of hydrogen embrittlement. If required by the product standard or purchaser, mechanical descaling or baking shall be performed to minimize this risk.

Baking should be carried out after pickling and before hot-dip galvanizing.