Understanding Fastener Materials
Fastener Tech Data | Understanding Series Introduction
When discussing fasteners, two terms you'll hear are ferrous and nonferrous. Ferrous means that the item is made from or contains iron: steel is considered ferrous. Conversely, nonferrous means that iron is not part of the item's composition: stainless steel, brass, silicon bronze and aluminum are all nonferrous. Nylon, by the way, is nonmetallic, because it isn't made with metal.
If strength is important, steel is a good inexpensive choice. If the fastener needs to be nonmagnetic, look to brass, silicon bronze and aluminum. For electrical conductivity, aluminum and brass are very good; nylon is a good electrical insulator. Aluminum and nylon are lightweight. To withstand low and high temperatures, stainless steel works well.
As you can see, fasteners (bolts, screws, etc.) are made in different ferrous, nonferrous and nonmetallic forms for different purposes. Sometimes you can interchange them, other times not. If you're replacing a fastener, it's often best to replace it with the same type. For other applications, use the chart below to guide your selection at Fastener Mart. If you are unsure of which type to use, seek professional help. And check our Understanding Platings and Finishes section for information about the corrosion resistance of various materials.
| Material | Characteristics |
|---|---|
| Steel | Magnetic and very common. |
| 304 Stainless Steel | May be slightly magnetic. Includes 18-8 Stainless Steel. |
| 316 Stainless Steel | May be slightly magnetic. |
| Brass | Nonmagnetic and softer than steel and stainless steel. |
| Silicon Bronze | Nonmagnetic and thermally conductive. |
| Aluminum | Nonmagnetic and one-third the weight of steel. |
| Nylon | Nonmagnetic, very lightweight and non-electrically conductive. Because nylon absorbs moisture, its dimensions and properties can change. Elevated temperatures can shorten useable life. |
Some materials are better than others with respect to resisting chemical corrosion. Generally speaking, there isn't one "perfect" material, so the final selection must be based on the specific application.
To assist in the selection, consider the information in these reference guides…
Be sure to visit our Fastener Tech Data section for even more information.