Surface finish is an important element in any specification or purchase order for stainless steel regardless of the intended end use. For those applications in which appearance is important, finish is a design element and must be specified. For those applications where finish is not so important, it should still be specified to avoid receiving a finish that is inappropriate for the application.

The purpose of this section is to help designers and specifiers achieve a better understanding of stainless steel finishes. The text describes and illustrates standard industry finishes and how finishes are applied to stainless steel.

Designers, specifiers and purchasing officials are also encouraged to contact ASSDA, a local stainless steel service centre or fabricator concerning any surface finish requirements.

Finish - A Design Element

There are several good reasons for paying close attention to the finish designation. In architecture or other highly visible applications, the appearance of stainless steel is a critical design element and a misunderstanding or the wrong finish can alter the desired effect. In consumer products such as appliances, cookware and automobiles, the gleam of well polished stainless steel has strong sales appeal. In commercial equipment, such as used in institutional kitchens, restaurants and hospitals, properly finished stainless steel helps to emphasise the feeling of cleanliness.

In addition to the visual appeal of polished stainless steel, there are a number of functionally important purposes served by properly prepared stainless steel surfaces. In sanitary applications, polished stainless steel not only looks clean, it is easy to clean and keep clean.

In aggressive environments, the smoother the surface, the better the corrosion resistance. A smooth surface is less susceptible to an accumulation of deposits which may become focal points for localised corrosion.

Finish and Fabrication

Some fabrication operations in manufacturing stainless steel products, such as deep drawing, may yield better results if the metal surface has a slightly rough texture to hold lubricants. Proper lubrication minimises tool wear, and it helps to reduce the severity of tool marks. In wire, the finish and coating serve to facilitate further steps in manufacturing such as cold heading of fasteners.

There are also economic considerations in specifying finish. For example, a cold rolled bright annealed finish might be specified instead of a more expensive No. 8 polished finish.

Relative comparison of grit size
Particle
size
inches
Particle
size
microns
All product other than emery Emery
Grading system Comparable
grit symbol
Polishing
paper
Cloth
CAMI FEPA
0.00026 6.5 1200 - - 4/0 -
0.00035 9.0 - - - - -
0.00036 9.2 1000 - - 3/0 -
0.00047 12.0 - - - - -
0.00048 12.2 800 - - - -
0.00059 15.0 - - - - -
0.00060 15.3 - P1200 - - -
0.00062 16.0 600 - - 2/0 -
0.00071 18.3 - P1000 - - -
0.00077 19.7 500 - - 0 -
0.00079 20.0 - - - - -
0.00085 21.8 - P800 - - -
0.00092 23.6 400 - 10/0 - -
0.00098 25.0 - - - - -
0.00100 25.75 - P600 - - -
0.00112 28.8 360 - - - -
0.00118 30.0 - P500 - - -
0.00137 35.0 - P400 - - -
0.00140 36.0 320 - 9/0 - -
0.001575 40.0 - - - - -
0.00158 40.5 - P360 - - -
0.00172 44.0 280 - 8/0 1 -
0.00177 45.0 - - - - -
0.00180 46.2 - P320 - - -
0.00197 50.0 - - - - -
0.00204 52.5 - P280 - - -
0.00209 53.5 240 - 7/0 - -
0.00217 55.0 - - - - -
0.00228 58.5 - P240 - - -
0.00230 60.0 - - - - -
0.00254 65.0 - P220 - - -
0.00257 66.0 220 - 6/0 2 -
0.00304 78.0 180 P180 5/0 3 -
0.00363 93.0 150 - 4/0 - Fine
0.00378 97.0 - P150 - - -
0.00452 116.0 120 - 3/0 - -
0.00495 127.0 - P120 - - -
0.00550 141.0 100 - 2/0 - Medium
0.00608 156.0 - P100 - - -
0.00749 192.0 80 - 0 - Coarse
0.00768 197.0 - P80 - - -
0.01014 260.0 - P60 - - -
0.01045 268.0 60 - 1/2 - -
0.01271 326.0 - P50 - - -
0.01369 351.0 50 - 1 - Ex. Coarse
0.01601 412.0 - P40 - - -
0.01669 428.0 40 - 1-1/2 - -
0.02044 524.0 - P36 - - -
0.02087 535.0 36 - 2 - -
0.02426 622.0 - P30 - - -
0.02488 638.0 30 - 2-1/2 - -
0.02789 715.0 24 - 3 - -
0.02886 740.0 - P24 - - -
0.03530 905.0 20 - 3-1/2 - -
0.03838 984.0 - P20 - - -
0.05148 1320.0 16 - 4 - -
0.05164 1324.0 - P16 - - -
0.06880 1764.0 - P12 - - -
0.07184 1842.0 12 - 4-1/2 - -

FEPA - Federation of European Producers of Abrasives
CAMI - Coated Abrasive Manufacturers Institute (USA)