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Stainless Steels
Classes of Stainless Steel
flash welding (2)
What is Flash Welding?

Stainless Steel Finishing Options

  • There are many stainless-steel finishing options that change more than just the appearance of the material. Whatever the intended use, choosing the right finish option is vital.
  • In projects where design is a major consideration, an attractive finish will enhance the appeal of the final product. For example, in the construction and automotive industries, different finishes can be used to achieve a variety of visual effects. 
  • Where manufacturing processes are applied, the choice of surface finish is also important. Where steel is ground prior to painting and bonding, a rough surface finish is appropriate. Where steel is mixed, a smooth surface finish is better.
  • The choice of surface finishing should always be clearly specified and correctly defined by standard industry names.

Development of Surface Finishing Standards

In the late 1970s, scientists at British Steel found that dull polished surfaces on stainless steel showed a wide range of surface roughness. Further tests showed that steels with high surface roughness were severely damaged during polishing operations, while those with a rough surface were relatively unscathed.

In the mid-1980s, dull polished finishes were widely used for projects such as high-profile architectural projects. However, it soon became apparent that some of these dull polished finishes had poor corrosion resistance, particularly when exposed to seawater. As a result, a new description of surface finishing was introduced, which is still in use today.

The three more common options for stainless steel finishing are:

  1. No. 2B – Matt finish
  2. No. 4 – Brushed finish
  3. No. 8 – Mirror finish
Stainless Steel Finishing Options

No. 2B - Matt Finish

No. 2B is a mill finish, which means that it has not been further worked. Matt finishes have a dull appearance and are not suitable for atheistic end uses. However, they are a good choice when appearance is not important or when further finishing is intended. These are the cheapest of the stainless steel finishes.

Finishes are produced from “cold rolled” stainless steel by means of special rolls or dies. Cold rolling produces a smoother, less pitting surface. Next, it is softened and descaled in an acid solution. The steel undergoes a final pass on polishing rolls to further improve its smoothness.

Common applications include:

  1. Chemical plant equipment
  2. Pharmaceutical plant equipment
  3. Paper mill equipment
  4. Laundry and dry cleaning services
  5. Refrigeration
  6. Waste water treatment equipment

No. 4 - Brushed Finish

  • No. 4 brushed finishes may vary from supplier to supplier, or even from batch to batch from the same supplier. These variations arise from different manufacturing conditions, such as the wear of the abrasive belts used in these finishes. Some degree of variation should be expected when ordering a No. 4 brushed finish. It may be helpful to request a sample of a few square inches to ensure the finish achieves the desired effect.
  • Brushing in stainless steel produces a unique appearance with a soft luster and a subtle pattern of parallel lines. It has a strong decorative appeal without being too reflective, as too much reflectivity may not be desirable. For example, excessively reflective stainless steel accents on buildings can be blinding in bright sunlight. Disadvantages of this include reduced corrosion resistance, as the grooves in the finish are prone to rusting.
  • The surface treatment is achieved by grinding the stainless steel in one direction with a 120-180 grit belt and then softening it with an 80-120 grit non-woven belt.
  • Common applications include:
  1. Jewlery and watches
  2. Home appliances
  3. Air Conditioning
  4. Water heaters
  5. Architecture
  6. Automotive design.
  • The Gateway Arch in St Louis, Missouri is the tallest arch in the world and is covered in brushed stainless steel.
  • The DeLorean DMC-12 sports car, famous for its appearance in the Back to the Future film, features brushed stainless steel paneling.

No. 8 - Mirror Finish

  • The mirror finish is highly reflective and is made from polished stainless steel. The polishing process enhances the appearance and consistency and makes cleaning easier. It also conceals the after-effects of welding and hides surface damage.
  • No. 8 The mirror finish is produced by mechanically treating the surface with a series of progressively finer abrasives. Alternatively, the appearance of mechanical wear can be simulated using a special rolling procedure. For this stage, deep scratches must be removed, as any surface defects are very visible on the finished product. The final process consists of polishing the surface for 5-10 minutes to produce a mirror-like, highly reflective finish.
  • A benefit of No. 8 Mirror finishing is that it improves corrosion resistance. The polishing eradicates crevices where corrosive particles can lodge themselves.
  • Common applications include:
  1. Mirrors
  2. Decorative trim
  3. Clean rooms
  4. Column covers
  5. Wall panels
  6. Reflections
Stainless Steel Finishing Options
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