Materials

 

 Carbon 

 Steel 

 Over 90 percent of all fasteners are manufactured using carbon steel. The reason is quite simple. Steel has excellent workability, offers the broadest range of attainable comparison with other commonly used fastener materials, it's inexpensive.

In general, use of carbon steel for fasteners can be catalogued into 3 broad groupings, low carbon, medium carbon, and alloy steel. They come in varying grades with variable strength characteristics. Click here to List Grades

 Stainless 

 Steel 

 All stainless steel contains some carbon, however carbon content is usually quite low and it's carefully controlled. Additionally all stainless steels have a mix of other alloying elements. Nickel is the most important. It dramatically improves corrosion resistance, adds toughness in low temperature exposures, and helps retain strength.
  • Austenitic Stainless Steel: About 80% of all stainless steel fasteners are produced from the austenitic grades, they are commercially nicknamed "18-8 Series" or "300 Series Stainless." They have better corrosion resistance than other stainless groups, and are non-magnetic. They are non-heat treatable, however they have excellent strength properties and toughness at extremely low temperatures. (Types 302, 303, 304, 305, 316, 321, 384)
  • Martensitic Stainless Steel: About 10% of all stainless steel fasteners are made using martensitic stainless steel, which are magnetic. The corrosion resistance offered by martensitic steels is not as good, or as versatile as other group, however in their heat-treated condition; they perform adequately in most atmospheric and marine exposures. (Types 410, 416, and 431)
 Brass  Used for corrosion resistance, and its thermal and electrical conductivity. Usually recognized for its yellow or gold coloring, and the most popular of copper alloys. Brass tends to be soft and not high strength, it is also non-magnetic.
 Bronze  Similar to brass in application but provides higher strength. Has more of a red/orange color to it.

 Aluminum 

 This dull silver or gray non-magnetic material is synonymous with lightweight. Aluminum fasteners weigh about one-third those of steel. The strength-to-weight ratio of aluminum fasteners is better than any other commercially used fastener material, but only the most common fasteners are available in this material.

 Nylon 

 This non-metallic plastic is lightweight, corrosion resistant, they have excellent thermal and electrical insulating properties, and they are easily colored for appearance, matching and identification.  To their detriment, plastics are low strength, they can't tolerate evenly moderately elevated temperatures, and many of them quickly embrittle in relatively low temperatures.
Please note there are a variety of other materials and variations within these types that are available.  Because they are infrequently specified they will not be covered here.

Corrosion Resistant Chart

 

Mechanical Properties & Grade Markings for Carbon Steel