1 Finish is produced by rolling stainless steel that has been heated prior to rolling (hot-rolling). This is followed by a heat treatment that produces a uniform microstructure (annealing) and ensures that the stainless steel will meet mechanical property requirements. This finish is mainly used for industrial applications such as furnace arch supports, furnace conveyors, furnace linings, air heaters, boiler baffles, incinerators, kiln liners, and industrial oven liners, among many others.
2B Finish is the term used by the ASTM A480 standard to define “a smooth, moderately reflective cold-rolled annealed and pickled or descaled finish typically produced by imparting a final light cold-rolled pass using polished rolls.” It is the most widely-used stainless steel finish available today. It’s often used for everything from flatware, bakeware, and pharmaceutical equipment to plumbing fixtures, sheet metal products, and solar collector panels.
2D Finish is a refined surface finish that is achieved by cold rolling, heat treating, and pickling. This is a uniform, dull silver-grey finish that is rougher than the 2B Finish. Pickling or descaling is necessary after heat treatment to remove the chromium-depleted dark surface layer and restore corrosion resistance. Applications include roofing, petrochemical equipment, and electric range parts.
4B Finish is produced by rolling the sheets of stainless steel between polished rollers. It commonly has a slightly matte or frosted appearance. The surface is usually very smooth but the Ra's can be all over the place and still meet the spec. It is often used on average restaurant or kitchen equipment, food processing or dairy equipment, and elsewhere.
Bright Annealed (BA) Finish is cold rolled stainless steel that is annealed in a controlled atmosphere to retain a highly reflective finish. Although it is not completely identical to the #8 mirror finish, it appears to be very similar. Applications include surgical instruments, fishing equipment, cookware, automobile trim, chute liners and textile finishing equipment.
Mirror Finish is a highly reflective, smooth finish with a scratch-free appearance, achieved through polishing the stainless steel. Also known as a #8 finish, a mirror finish can be achieved mechanically, using a progressive series of abrasives and polishing compounds. The application includes clean rooms (countertops, wall panel doors, handles), food processing, pharmaceutical, life science operations, and machinery that must remain sterile (medical equipment manufacturing, pharmaceutical manufacturing, food processing, and brewing.)