Surface finish is an important element in any specification of stainless steel regardless of the intended use.
For those applications where appearance is important, finish is a design element and must be specified.
In non-decorative applications the surface finish may have implications for friction, wear, maintenance or corrosion resistance and must, therefore, also be carefully chosen and clearly specified.
The choice of finish should never be left to the supplier, or the specification loosely worded, such as “Type 304 with a 180 grit finish”.
The finish should be properly identified by a standard industry designation or by a trade name, e.g. OPTISHEEN®.
Aalco has available a sample swatch of stainless steel finishes including 2B, Bright Annealed (2R) plus various polishes including OPTISHEEN® and Circle Polished - Please contact your local Service Centre to view one. (http://www.aalco.co.uk/datasheets/Stainless-Steel-Stainless-Steel-Finishes-Sample-Swatch-Sheet_420.ashx)
Finishes and Design
There are a wide range of decorative finishes available; therefore, it is important to pay close attention to the selection of the most appropriate finish for the application required. For highly visible applications the appearance of stainless steel is a critical design element and a misunderstanding of the wrong finish can alter the desired effect. In commercial and hygienic applications, such as restaurants and hospitals, properly finished stainless steel is easier to keep clean. In consumer products, such as catering equipment, the lustre from a well polished sheet of stainless steel has strong sales appeal.
In addition to the visual appearance of polished stainless steel there are a number of functional considerations. In sanitary applications correctly polished stainless steel not only looks good but it helps to reduce the risk of bacteria being retained by the material.
In aggressive environments, such as in the nuclear or offshore industries, a correctly polished stainless steel surface has a better resistance to corrosion than a surface that is roughly or badly polished. A smooth surface is less susceptible to an accumulation of deposits and stainless, which often become focal points for localised corrosion. All stainless steel finishes perform better when cleaned and maintained and details of correct cleaning procedures may be found in our publication, “The Cleaning and Maintenance of Stainless Steel”.
Finishes and Fabrication
Some fabrication operations, such as grinding prior to painting or gluing, may require a rough surface finish but, generally speaking, a smooth, well finished sheet requires less physical effort than a coarse, rough one when it comes to blending. Certain finishes are more difficult to recreate by hand than others, causing fabrication difficulties; this is especially true of the “special” finishes which cannot be easily replicated in a fabrications workshop. For this reason the fine satin finish (such as Optisheen®) is popular and practical for fabrication shops around the world.
The term “polished” defines a range of finishes which generally are of two types, either: (a) satin or grained or (b) brightened and mirror polished. Polishing improves appearance and consistency, make cleaning easier and aids practicality to fabricate and repair/blend after welding and to mask minor damage. Satin Polished stainless steel is practical in use, widely available, relatively low cost and the most commonly used.