Choosing a stainless steel finish is about more than just how the finished product looks. The finish you choose for your stainless steel products can have an impact on the performance as well as the visual aspect of the design.
For this reason, choosing the right finish for your application from the stainless steel finish options is vital. This stainless steel finishes guide will look at the different stainless steel finishes and how they will affect your finished product.
Mill Finishes
The natural finish of Stainless steel depends on what product is being produced (Sheet, Bar, Tube etc) and the production method. Here we take a look at the natural Mill finishes.
1D Finish - Hot Rolled, Annealed & Pickled
This process requires the steel to be hot rolled through a mill before going through a heat treatment process called annealing. This consists of the steel being heated and then cooled slowly to reduce hardness and internal stress. This is required to ensure the steel is easier to work with. Pickling is the last step and involves removing any scales that have formed during the heat rolling and annealing processes.
2D Finish – Cold Rolled, Annealed & Pickled
The 2D surface finish is similar to the 1D finish except as it is cold rolled, not heat rolled, the process is more refined, but the pickling art of the finish is essential due to the cold rolling to give the required finish. Again as with 1D finishes, the 2D finish can be a base for additional finishes.
2B Finish – Cold Rolled, Annealed, Pickled & Skin Passed
Similar to the 2D process, the 2B finish follows the same procedures except for an additional step. This extra step produces an average roughness between 0.1 and 0.5 micrometres to give a smooth, more consistent finish. 2B is the most commonly used material when mechanically polishing.
2R Finish – Cold Rolled, Bright Annealed & Skin Passed
The 2R finish is typically used for household appliances and applications such as builders' materials and for uses where reflection is essential. Again, the process for the 2R finish follows the same production methods; however, the skin-passed aspect consists of annealing the steel in oxygen-less conditions. This protects it from oxidation and scaling, giving it an easy-to-clean finish. The semi-reflective surface of a bright annealed product makes it a better choice for reflective mechanical polishing such as Bright or Mirror polishing.
Mechanically Polished Surfaces
Stainless Steel is often used in applications that need it to be aesthetically pleasing or easy to clean and free from contaminants. Mechanical polishing is often a process used to achieve this.
The surface of the product is mechanically polished and brushed for this method to achieve standard finishes. The surface is processed with abrasive materials that effectively create a consistent finish, within set tolerances.
Different factors influence the surface finish of mechanically polished and brushed stainless steel. These factors include the original surface (starting point), the type and texture of polishing belts and brushes used, and the nature of the polishing process. Here we look at a few examples of mechanically polished material.
Grained finishes
More commonly known as Dull Polished, polishing belts consisting of an aluminium oxide abrasive create a unidirectional grain along the sheet. The process also removes any minor surface defects.
There’re various different grained finishes, such as 240G, 240S and satin polished.
The polished finish will confirm within a specific Ra reading based on a 2B finish being initially used. Depending on the specification of the grain that’s required, the finished product will look subtly different from a different specification. It’s important to know exactly what polish you require, particularly if matching to an existing product.
Dull polishing is widely used in the catering, architectural and pharmaceutical industries.
Reflective finishes
More commonly known as bright, or mirror polished. The reflection is produced using mops and compounds. Similar to Dull polishing, there are different levels of finish that will conform within tolerances of Ra readings and reflectivity. As the process is less invasive on the natural finish of the sheet, it won’t always remove any surface defects.
The reflective finish makes it ideal for trims and signage but also the smoothness of the surface means less contaminants which make it ideal for Marine and pharmaceutical applications.
Circular finishes
Circle polishing is achieved from a series of circular abrasive heads creating a continuous pattern by overlapping on the surface of the product. The process removes very little of the original surface, so any imperfections in the material may not be removed. The pattern can be varied to your specification and is commonly used in the catering and architectural industries.
Stainless Steel Coloured Finishes
There is an inert chromium layer at the surface of the stainless steel, which is corrosion-resistant and allows for a coloured finish to be applied. Chemical processes colour this chromium layer before being hardened by electrical methods. Coloured stainless steel finishes are also able to be patterned too. Many colours and designs are available to those wishing for coloured stainless steel finishes; however, the universal designation is 2L Stainless Steel Finish.
If you wish to learn more about the stainless steel finishes guide to help you learn more about the correct type of finish for your needs, then contact our knowledgeable team, who can help you get the right product.
Feel free to contact our team at Leengate Metals for any advice based on the specifications of your project.