Selecting the right bolt is an important aspect of any bolted flange connection. And, to ensure a reliable seal, selecting the correct coating option for bolts can be just as important. While there are many different coating options available, zinc, cadmium, and PTFE are three of the most popular.
When selecting a bolt for a flanged connection, there are three key properties to consider: 1) strength, 2) temperature range, and 3) corrosion resistance. ASME B16.5, the standard for “Pipe Flanges and Flanged Fittings” (1/2” to 24”), specifies the bolt diameter for each flange. However, the bolt material of construction and type/class must still be determined. Regarding strength, the bolts must be strong enough to compress the gasket sufficiently to create a seal without breaking or deforming. Table 1.1-2 in B16.5 lists some bolting materials and their specifications.