A325 galvanized bolts are heavy hex structural fasteners with a hot-dip zinc coating for outdoor steel in wet, salty, or corrosive service. The medium-carbon core is quenched and tempered, then dipped in molten zinc so the coating fuses to the steel rather than sitting on it. Bridges, coastal structures, and exposed framing specify A325 galvanized bolts where bare steel would need repainting within a few years.
Products Key Features
Fused Zinc, Not Paint
The A153 Class C coating runs about 2 mils (50 µm) and metallurgically bonds to the steel. It penetrates threads and inside corners that spray-applied coatings miss, and it does not peel or flake.
01
120 ksi Quenched-and-Tempered Core
Minimum tensile is 120 ksi (827 MPa) on diameters through 1″ and 105 ksi (724 MPa) on 1-1/8″–1-1/2″, with yield at 92 ksi (634 MPa) up to 1″ and 81 ksi (558 MPa) above. A325 galvanized bolts deliver full code-compliant pretension in slip-critical and bearing-type joints.
02
Heavy Hex Head, Grade-Marked
The head pattern seats fully under a structural wrench or socket, and the A325 grade mark plus maker's symbol remain legible after galvanizing, so inspectors read the bolt's identity at a glance.
03
Self-Healing Zinc
Where the coating is scratched or a thread is cut, the zinc around the damage corrodes first and shields the exposed steel underneath. A scratch through paint turns into a rust line; a scratch through hot-dip zinc does not.
04
Wax the Threads Before Tensioning
RCSC requires wax lubrication on galvanized threads before pretensioning. The zinc surface grips harder than bare steel, so an unlubricated joint reads high on the torque wrench while it stays under-tensioned. This step belongs to galvanized A325 bolts only.
05
Products Specifications
|
Item |
Specification |
|
Product Name |
A325 Galvanized Bolt / A325 HDG Structural Bolt |
|
ASTM Designation |
ASTM F3125 Grade A325 (formerly ASTM A325) |
|
Coating |
Hot-dip galvanized, ASTM A153 Class C, ≈2 mils (50 µm) |
|
Material |
Medium carbon steel, quenched & tempered |
|
Tensile Strength |
120 ksi (827 MPa) min, 1/2″–1″; 105 ksi (724 MPa) min, 1-1/8″–1-1/2″ |
|
Yield Strength |
92 ksi (634 MPa) min ≤1″; 81 ksi (558 MPa) min, 1-1/8″–1-1/2″ |
|
Thread |
UNC, Class 2A |
|
Head Type |
Heavy hex |
|
Nut |
A563 Grade DH heavy hex, HDG, over-tapped |
|
Washer |
F436 Type 1, HDG |
|
Sizes |
1/2″ to 1-1/2″ (nine diameters) |
|
Lengths |
1-1/2″–6″ (custom on request) |
Products Applications
Bridges & Highways - girder splices, bearings, and barrier/handrail connections. A325 galvanized bolts fasten steel that never dries out.
Coastal & Marine - wharves, jetties, and dockside framing in salt spray.
Outdoor Utility Steel - transmission towers, sign gantries, and pipe racks in open exposure.
Corrosive Industrial - water and wastewater plants, chemical facilities, and paper mills.
FAQ
Q: How long does the hot-dip coating last?
A: Service life tracks coating thickness and local corrosivity. A 2-mil A153 Class C coating typically delivers 50+ years before first maintenance in rural or suburban exposure, and 20–30 years in industrial or marine air. In practice, the zinc often outlasts the structure's design life.
Q: What pretension should A325 galvanized bolts reach?
A: Minimum pretension runs from 12 kips at 1/2″ to 103 kips at 1-1/2″ - 12, 19, 28, 39, 51, 56, 71, 85, and 103 kips across the nine diameters. Values assume wax-lubricated threads per RCSC.
Q: Black or galvanized - how do I decide?
A: Galvanized when the steel sees weather, salt, or standing moisture. Black (plain) when the joint is interior and will be painted or fireproofed. A325 galvanized bolts cost a premium per bolt, but they remove a lifetime of touch-up paint and replacement labor on exposed steel.
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