Stainless steel finishes offer a range of benefits. You can think about finishing as a fabrication process applied to enhance the metal’s surface character. Whether you need durability, corrosion resistance, a reflective surface, smoothness, or a specific grain pattern, any are available and desirable depending on the ultimate end use.
Now, there are over 150 unique grades of stainless steel. Stainless steel sheet, stainless steel plate, stainless steel bar, and stainless steel tube all find their way into an impressive range of industries. In fact, from the architecture industry to the automotive industry, stainless steel finishes help to achieve different visual and mechanical effects that will meet wide ranging needs.
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What are the different types of stainless steel finishes?
Stainless finishes fall into three main categories: mill finishes, brushed and polished finishes, and bright annealed and temper rolled finishes.
Mill finishes produce matte finishes that are most suitable for industrial uses and when a smooth surface is not required. Usually, mill finishes are selected for end uses where durability remains the highest priority.
Brushed and Polished Finishes
Brushed and polished finishes are mechanically achieved. These finishes are considered more abrasive than mill finishes. The surface finishing outcome depends on the steel’s starting point—for instance, how rough or uniform the surface is—and which belts, brushes, and polishing process is selected. Grinding is one of the more common brushed and polished finishing techniques and will produce a more refined surface.
Other variables that will affect the end surface include the amount of time the metal is in contact with the brushers and the amount of pressure.
This type of stainless steel finish produces a highly reflective and polished finish. It is the ideal choice for aesthetic and ornamental applications.
Bright Annealed (BA) and Temper Rolled (TR)
Bright annealed finishes are produced by heat treating the stainless steel. The annealing processes is closely monitored in a controlled atmosphere or with vacuum protection. Once the stainless is heated to melting point, it is rapidly cooled. The end goal is a more corrosion resistant product that maintains good weldability and smoothness. As the name suggest, this finishing process leads to a brighter surface quality.
One of the main advantages of this kind of stainless steel finishing process is its protective layer which improves cleanliness, as it prevents oil and oxide adhesion.
What are the most popular mill finishes?
There are three very popular mill finishes: No. 1 stainless steel finish, 2B stainless steel finish, and 2D stainless steel finish.
No. 1 stainless finish
No. 1 mill finishes are achieved by hot rolling the stainless steel to a desired thickness. They tend to look dark and varied, and demonstrate the roughest, least uniform surface character of all of the stainless steel finishes. They do not have a reflective nature. Typically, No. 1 mill finishes are selected when aesthetic appeal is the lowest priority. Often, No. 1 finishes are followed up with a pickling process which will strengthen the corrosion resistance. One of the main disadvantages for this type of finish is that it does not have a reflective surface and will only be useful for applications where look, feel, and brightness are not required.
Some of these applications include:
- air heaters
- furnace parts
- gas turbines
2B stainless steel finish
2B stainless steel finish is perhaps the most popular stainless steel finish. This cold roll finish produces a clean matte finish. It’s mainly non-reflective and smooth with excellent evenness. The stainless steel is annealed and pickled following the cold rolling process. After this, 2B stainless steel passes through “bright rolls.” This extra step gives 2B its characteristically smooth, flat surface.
Examples of applications with 2B stainless steel finish include:
- solar panels
- chemical and pharmaceutical equipment
- laundry components
- refrigeration parts
- food processing equipment
2D stainless steel finish
2D stainless finish relies on a similar processing technique to 2B stainless steel finishes. Though it is also cold rolled, annealed and pickled, 2D stainless steel finishes maintain a duller, matte finishing quality.
2D stainless steel finishes show up in:
- gutters and other drainage components
- railcar parts
- vehicle exhaust systems
- petrochemical equipment
Why are 2B and 2D pickled and annealed?
You might wonder, “What is annealed metal?” or, “How does annealing effect stainless steel?” and these are great questions! Both 2D and 2B stainless steel finishes are annealed in order to counter some of the effects caused by the cold rolling process. In short, annealing removes stress and reduces hardness. Pickling is then needed to level out the finishing character by removing any impurities caused by the annealing process.
What are the most popular brushed and polished finishes?
There are three main types of brushed and polished finishes: #3, #4, and #8 (Mirror Finish).
#3 stainless finish
#3 finish is a brushed finish achieved by rough grinding. This finishing process typically yields a surface finish that is coarse, unidirectional, and low to non-reflective. The material grade as well as the type and quality of grinding belt, will impact the amount of surface roughness.
This stainless steel finish is often used for:
- food processing and brewery equipment
- kitchen appliances
#4 stainless finish
#4 finish produces a more refined surface. It is processed with polishing belts and brushes that will still result in a mildly reflective and one-directional surface quality. The ultimate roughness is determined by the brush grade, and quality of the polishing belt.
#4 finish is known to have a distinct look characterized by a muted color and very fine lines. It suits many decorative needs. However, only those that do not require reflectiveness. One of the main drawbacks for this kind of stainless steel finish is its reduced corrosion resistance.
As a result, it’s always recommended to confirm with your metal supplier and metal fabricator to ensure that the stainless finish meets your requirements.
This type of finish is best suited for:
- AC units
- indoor decorative architectural elements
- cars and trucks
#8 stainless finish (Mirror finish)
#8 stainless finish is also commonly referred to as “mirror finish” because of its highly reflective nature. So much so that the stainless steel mimics the appearance of a mirror. This finish requires additional buffing, usually somewhere between five and ten minutes. This extra polishing time results in nearly invisible line quality. Any imperfections are removed.
Here are some of the popular applications for this finishing process:
- sculptural components
- plating and wall paneling
What are some common stainless steel grades and finishes?
Two of the most common stainless steel grades are 304 and 316. They can undergo various finishing processes, including #2B, #2D, #3, #4, and bright annealed.
Kloeckner Metals routinely stocks the most popular stainless steel grades in a range of stainless steel formats with the highest quality finishes. You can click to learn about different stainless steel grades and the different types of stainless steels or reach our sales team today to discuss your project’s requirements.
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