The surface finish of stainless steel is a very important factor in improving the functionality as well as the appearance of the application.
The desired surface finish also has a better effect on the properties of the end product, like corrosion resistance, electrical conductivity, weldability, and manufacturing procedures.
The surface finish of stainless steel is a primary consideration in designing the products to enhance the attractive look of the end product.
Different finishes can be utilized to generate a range of visual effects in the architecture and automobile industries. For example, the stainless steel No. 4 finish is one of the most popular finishes available in everyday products, particularly kitchen appliances.
The surface finish chosen is especially significant where fabrication procedures will be used.
When the stainless steel sheets or plates are grounded before painting and bonding, rough surface treatments are suitable. Where the steel is to be mixed, smooth surface finishes are preferable.
The finished surface should always be clearly stated and correctly defined by industry standards. If you want more information about surface finishes, keep reading below article guide to learn all the types of surface finishes.
What Is A Stainless Steel Surface Finish?
The physical appearance of the stainless steel is formed through various processing procedures such as rolling, polishing, and blasting.
These finishes can vary from dull to bright; some even have specific textures that may be applied mechanically for specific uses.
Surface finish can be affected by a variety of elements, including production route, material thickness, roll surface polish, cleanliness, and mechanical abrading.
Most melt mills are capable of producing all sheets and strip finishes. While some finishes (such as BA and polished) necessitate specific lines, most mills either have these or work with a third-party processing partner.
Still, melt mills can only sometimes meet each customer’s specific Ra (surface roughness) criteria.
Some customers may need a precision re-roller to achieve their required surface finish.
What Are The Different Types Of Stainless Steel Surface Finishes?
The surface finishes are categorized by the special process routing in the industry, not only the appearance of the surface.
It means surface finish can be categorized by the process or stage from which it is being passed.
There are different standards and procedures for the strips and sheets. If the dimension of the piece is more than 24 inches wide, it is called a sheet, and less than 24 inches is known as a strip.
Some common types of surface finishes are given below.
Mill Finish No. 1
This type of surface finish is known as the basic type of finish. It can be produced by hot rolling processes and used in many stainless steel products.
They are widely utilized in a variety of applications and serve as the foundation for mechanical polishing and other finishing procedures.
Most are cleaned with acid (pickled) to get rid of the scale that creates up during hot rolling and annealing to maximize corrosion resistance.
Finish No. 2B
The 2B stainless steel finish is the most common stainless steel finish.
This cold roll finish yields a smooth matte surface. It’s mostly non-reflective and smooth, with good evenness.
Following the cold rolling process, the stainless steel is annealed and pickled.
After this, 2B stainless steel is passed through “bright rolls.” This extra step gives stainless steel a distinctive smooth, flat surface.
Finish Bright Annealed (BA)
Finish the bright annealed surface obtained by the cold rolling process.
After this process, apply the annealing in a controlled atmosphere to avoid scaling.
This finish is not treated in acid since annealing produces a thin oxide film that eliminates the requirement for pickling.
This type of finish is used in trim appliances, medical tools, and cookware.
Finish Mechanically
In this type of surface finish, some abrasive tools are used, such as grinding and polishing tools, to cut the material to get the required surface finish.
Very thin and high-quality abrasive is used to polish the surface.
Polished Finish No. 3 & No. 4
Surface finish no.3 and no.4 are achieved by the brushing process.
This process consists of one-directional uniform parallel line along the length of the coil.
Finer abrasives are used to achieve a polished finish.
The range of grit abrasives is 50 to 120 for the No.3 finish and 120 to 320 for the No.4 surface finish.
Finish No. 6
Finish No. 6 is much less reflective than the No.4 finish.
It is very dull, and its color is silvery white.
This type of surface finish is a very old technique and is not commonly used on stainless steel these days.
Finish No. 8 Finish
This type of surface finish is a more reflective polished surface than all finishes recommended by the ATSM standards.
The No. 8 Finish is obtained by buffing for five to ten minutes longer than the No. 7 Finish.
The No. 8 finishes stainless steel sheets are commonly seen in high-end luxury hotels, museums, and office buildings for interior decorative applications such as panels or columns.
What Is The Surface Roughness Of Stainless Steel?
The texture measurement of manufactured or polished surfaces is called surface roughness. It is the average distance between the peaks and valleys of the polished surface.
It is measured in micrometers or micro inches and written as “Ra” average roughness.
Rz, or mean roughness depth, is the average of the lowest valley to the highest peak across five sampling lengths and is most typically used in Europe.
Surface roughness can significantly impact the durability and performance of a material and must be carefully addressed and regulated.
Conclusion
Taking all the factors into account, all the grades of surface finish are important for the attractive appearance and functionality of stainless steel.
After reading this guide, you will understand all the types and techniques of surface finishes.
Now, if you have any doubts regarding your application’s surface finish, feel free to contact us.
Our experienced staff is always ready to assist you in selecting the right surface finish of stainless steel for your project.
