Stainless steel is a unique metal alloy composed of steel (iron/carbon) and chromium. There are a variety of finishes that can be applied to stainless steel, from standard mill finishes, to specialty finishes such as brushed, polished, etched, and bead blasting. Corrosion resistance is a determining factor for a stainless steel finish. Generally, the rougher the surface finish, the lower the corrosion resistance.
The most common stainless steel finish is 2B. This method is cold rolled, heat-treated, pickled and pinch-passed, resulting a slightly reflective surface similar to a cloudy mirror. The 2B mill finish is achieved with an additional light cold roll pass, and is the standard finish for 201, 301, 304, 304L, and 316L stainless steel. Stainless steel with a 2B finish is generally used for bakeware and flatware, plumbing fixtures, solar panels, industrial equipment, and wheel covers.
A No. 4 finish is sometimes called the workhorse finish, as it is easy to maintain in high-traffic areas such as handrails, kitchen equipment, stainless steel sinks, bus shelters, elevator doors, and work surfaces. Stainless steel with a No. 4 finish is attained by mechanically polishing the metal with fine abrasives belts to remove minimal amounts of metal from the surface. The resulting appearance has short, parallel lines for a linear effect. No. 4 finished stainless steel will appear different from manufacturer to manufacturer due to different belts and grit sizes, which usually range from 120 to 320 grit, depending on the project requirements. The higher the grit, the finer the lines and the more reflective the surface will be. No. 4 finished stainless steel is duller than stainless steel with a 2B finish.