• Hex bolts, or hex cap screws, are used in machinery and construction. Can be used with a nut, or in a tapped hole. Fully threaded hex bolts are also known as tap bolts
• Wood screws have large threads and a smooth shank for pulling two pieces of material together. They can be used in wood and other soft materials
• Sheet metal screws have sharp points and threads, and are designed to be driven directly into sheet metal. They can also be used in softer materials like plastic, fiberglass, or wood.
• Machine screws are fully treaded for use with a nut or in a tapped hole. Certain types are sometimes referred to as stove bolts.
• Socket screws are machine screws with an internal hex socket (Allen) drive. Longer lengths may have a smooth shank.
• Lag bolts, or lag screws, are large wood screws with hex heads. Typically used for wood construction and landscaping.
• Carriage bolts have smooth, domed heads with a square section underneath that pulls into the material to prevent spinning during installation.
• Nuts are used to fasten machine threaded fasteners in through-hole applications. Lock nuts help prevent loosening.
• Washers spread the load over a greater surface area when tightening a bolt, screw or nut. Lock washers help preventing loosening.

With regard to the flange bolt corrosion problem currently being addressed, and the possibility of using alternative bolting material, I will begin with a listing of bolting material that is acceptable to use with ASME B16.5 flanges, as defined by ASME B16.5-Pipe Flanges and Flanged Fittings. While the fluid service applications in your facility will only require a select few of the listed bolting materials I thought it might be helpful to see the scope of what is allowed by Code, with regard to material.