No. 1/HRAP
A moderately rough and dull surface, a No. 1 Finish involves rolling stainless steel that has been heated prior to rolling (hot-rolling). This is accomplished by a heat treatment that produces a uniform microstructure (annealing) and ensures that the stainless steel will meet mechanical property requirements. The resulting surface contains a dark non-uniform appearance where surface chromium has been lost, and the expected level of corrosion resistance has been achieved. A No. 1 finish may contain shiny spots were surface imperfections were removed by grinding. It is generally used in industrial applications, such as equipment for elevated temperature service.
No. 2B
A No. 2B finish is the most widely used stainless steel surface finish and is produced very similar to the No. 2D finish. Cold rolled, heat treated, pickled and pinch passed – this is a bright cold rolled finish except that the final light cold rolling pass is done using polished rolls. The result is a more reflective finish that resembles a cloudy mirror. It is especially common in industrial, chemical and food processing applications but also used in some architectural applications that will not be closely examined for uniformity of finish.