F436 Washer Type 1 vs Type 3
Choosing the Right Material
Hardened washers under ASTM F436 come in two material types, and the right one depends on the assembly and the environment. Type 1 is carbon or alloy steel for standard structural work; Type 3 is weathering steel for weathering-steel assemblies. The washer material should be compatible with the bolt and nut in the connection.
Type 1, Carbon Steel
Type 1 hardened washers are carbon or alloy steel, used for general structural applications with standard, non-weathering bolt assemblies. They are available in both plain and hot-dip galvanized finishes, which makes them suitable for painted, galvanized, and standard structural steel connections. Type 1 is the material used on the majority of structural connections, where the surrounding steel is not weathering grade and corrosion is managed through coating or galvanizing rather than through the steel chemistry itself.
Type 3, Weathering Steel
Type 3 hardened washers are weathering steel, intended for weathering-steel structural bolt assemblies where atmospheric corrosion resistance and a uniform weathered appearance are required. Type 3 washers are typically furnished plain rather than galvanized, because the weathering steel is designed to form its own protective oxide layer over time. Using a Type 3 washer with a weathering-steel assembly keeps the washer consistent with the surrounding steel, both in corrosion behavior and in the way it weathers visually, which matters on exposed architectural and bridge structures.
Why Matching Matters
Mixing material types in a single assembly can create a mismatch in corrosion behavior or appearance. A galvanized Type 1 washer used on an exposed weathering-steel connection, for example, will not weather to match the surrounding steel, and can behave differently in the environment the assembly was designed for. Selecting the washer type to match the bolt, the nut, and the connected steel keeps the whole assembly consistent.
Quick Selection
| If your structure uses… | Specify |
| Standard structural steel, painted steel, or galvanized steel | Type 1 |
| Weathering, atmospheric-corrosion-resistant steel | Type 3 |
Important: Match the washer material type to the bolt and nut material types used in the assembly.