Stainless Steel Finishes
STAINLESS STEEL FINISHES
Overview Of This Article
- STAINLESS STEEL FINISHES
- Introduction to Stainless Steel Finishes
- Types of Stainless Steel Finishes
- Mill Finishes Explained
- Polished and Brushed Finishes Explained
- Patterned and Coloured Finishes Explained
- Stainless Steel Finishes: The Conclusion
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Introduction to Stainless Steel Finishes
Choosing the finishes of the Stainless Steel material is an important part of purchasing and manufacturing. A wide variety of options are available when it comes to the Stainless Steel Finishes. The several types of finishes also affect the pricing factor as per the amount of labour and extra work the manufacturer or stockist has to input. There are different standards that offer their own designation for each type of stainless steel surface finish. You are probably looking for a long lifespan, corrosion resistance and low maintenance needs. The right finishing is the way to guarantee that stainless steel will behave as expected.
Types of Stainless Steel Finishes
Here is a comparision of the stainless steel finishes as per EN and ASTM standards in a table format. This gives you a deep explaination and great overview of the possibilities using both standards. In-depth details of each stainless steel finishes are discussed later in this article.
Mill Finishes
| EN | ASTM | DESCRIPTION |
|---|---|---|
| 1D | No. 1 | Hot rolled, heat treated and pickled. Rough surface but free of milling scale. |
| 2B | No. 2B | Cold rolled, heat treated, pickled and skin passed. Smooth surface. |
| 2D | No. 2D | Cold rolled, heat treated and pickled. Smooth surface. |
| 2H | TR | Work hardened. Cold worked for higher strength. Bright surface. |
| 2Q | - | Cold rolled, bright annealed and skin passed. Smooth, bright and reflective surface. |
| 2R | BA | Cold rolled, hardened and tempered. Scale free surface. |
Polished and Brushed Finishes
| EN | ASTM | DESCRIPTION |
|---|---|---|
| 1G-2G | No. 3 | Ground. Grade of grit or surface roughness can be specified. Unidirectional texture, not very reflective. |
| 1J-2J | No. 4 | Brushed or dull polished. Grade of brush, polishing belt or surface roughness can be specified. Unidirectional texture, not very reflective. |
| 1K-2K | No. 6 | Satin polished. Additional specific requirements to a J-type finish for adequate corrosion resistance in marine and external architectural applications. |
| 1P-2P | No. 7-8 | Bright polished. Process or surface roughness can be specified. Non-directional finish, reflective with a high degree of image clarity. |
Patterned and Coloured Finishes
| EN | ASTM | FINISH | DESCRIPTION |
|---|---|---|---|
| 2F | No. 2D | Patterned Finish | Cold rolled, heat treated, and skin passed on roughened rolls. Bright annealing or annealing and pickling. Uniform non-reflective matt surface. |
| 1M | - | Patterned Finish | Design upon agreement. One side is flat. Plates used on floors. |
| 2M | - | Patterned Finish | Design upon agreement. One side is flat. Fine texture is mainly used for architectural applications. |
| 2W | - | Patterned Finish | Design upon agreement. Both sides with corrugated texture, used to increase strength and/or for aesthetics. |
| 2L | - | Coloured Finish | Colours upon agreement. Colour is obtained by a chemical process. |
| 1S-2S | - | Surface Coating | Generally coated with tin, aluminium or titanium. |
Mill Finishes Explained
Mill finish is the basic supply condition for stainless steels, no matter whether they are cold or hot rolled. However, most of these steels require further finishing processes to meet the requirements of certain applications. Here is an in-depth description of the stainless steels finishes that fall into this group according to the table above.
EN 1D - ASTM No. 1 Stainless Steel Finish
After the stainless steel is hot rolled in the mill, it is then put through a heat treatment called annealing. Annealing consists of heating the steel and letting it cool down slowly to remove internal stress and reduce hardness. This makes it more ductile and workable.
After the annealing process, the 1D stainless steel is ready for the last step to achieve the designated finish – pickling. This process consists of cleaning the surface with acid to remove the scales. Scales form during the previous processes, hot rolling and annealing. The resulting surface is slightly coarse with very low reflectivity. A typical average roughness (Ra) between 4-7 micrometers.
1D stainless steel finish is sometimes used as the starting point for polished finishes. However, common applications of this stainless steel surface finish involve non-decorative purposes. Thus, the visual appearance is not always relevant. Some examples include:
- Unexposed Support Systems
- Structural Applications
- Air Heaters
- Furnace Conveyors
- Heat Exchangers
- Oil Burner Parts
EN 2B - ASTM No. 2B Stainless Steel Finish
Another cold rolled stainless steel where the process is similar to producing 2D. The difference is that there is an extra step in producing 2B stainless steel surface. That step is rolling it one final time with highly polished rolls known as bright rolls.
The typical average roughness obtained is between 0.1 and 0.5 micrometers. So the result is a smooth, slightly to moderately reflective surface with good flatness control.
Due to its dull grey and not very reflective appearance, it is only used in architecture when uniformity of finish is not a requirement. Common applications for the 2B stainless steel finish include, but are not limited to:
- Baking Equipment
- Refrigeration
- Food Processing Application
- Tanks and Vessels
- Vacuum Drum Dryers
- Solar Collector Panels
- Pharmaceutical Equipment
EN 2D - ASTM No. 2D Stainless Steel Finish
As this steel is cold rolled rather than hot rolled, the surface finish is more refined. The annealing and pickling processes improve its characteristics in a similar way as with the 1D stainless steel surface finishes. In this case, pickling is necessary because annealing is performed to remove stress and reduce the hardness resulting from cold rolling.
The surface finish has a low reflective matt appearance with typical average roughness values ranging from 0.4 to 1.0 micrometers.
Similarly to the 1D surface finish, the 2D can be the starting point for polished finishes. It can also be used for some industrial and engineering needs with less critical aesthetics. Common applications for 2D stainless steels are:
- Railcar Parts
- Automotive Exhaust Systems
- Builders’ Hardware
- Chemical Equipment
- Electric Range Parts
- Stone Anchors
- Roof Drainage Systems
- Petrochemical Equipment
EN 2R - ASTM No. BA Stainless Steel Finish
Again, there is only a small difference with previously described surface finishes. In this case, we have the bright annealing process added. It consists of annealing the steel under oxygen-free conditions to protect it from oxidation and scaling.
The resulting stainless steel finish is capable of reflecting clear images. It is very smooth and less likely to harbour airborne contaminants and moisture compared to any other mill finishes. This easy-to-clean finish has a typical Ra between 0.05-0.1 micrometers.
The 2R, also known as BA stainless steel, is commonly used for domestic applications. Also for applications where reflection is important but its precision is not. Some examples are:
- The inner part of Washing Machines and Dishwashers
- Commercial Refrigerators
- Food Processing Equipment
- Builders’ Hardware
- Surgical Instruments
- Highway Truck Trailers
- Road Mirrors
EN 2H - ASTM No. TR Stainless Steel Finish
This one is a little different from the rest of the mill finishes. Here, the metal is cold worked after the cold rolling process in order to obtain improved strength. The hardening is done by means of temper rolling on polished rolls. 6 different levels of strength are available depending on the yield strength, tensile strength and elongation.
The result is a fairly smooth reflective finish. Surface roughness for the 2H stainless steel finish is defined by manufacturers and it depends on the temper rolling process. The most common applications of the 2H stainless steel finish include:
- Automotive Applications
- Chains
- Machines and Instruments
- Press Plates
- Surgical Instruments
- Implants
- Stamping Parts
Polished and Brushed Finishes Explained
A few recommendations apply when selecting a stainless steel finish for your application. As a starting point, choose a mill finish that is the closest to the desired outcome. This way, the number of additional processes can be minimised. However, there are standard stainless steel finishes that are achieved by mechanically polishing and brushing the surface. This means that the surface will be processed by using abrasive materials that effectively cut the surface of the steel to a desirable degree.
The resulting surface finish for mechanically polished and brushed stainless steels will depend on different aspects. Those include the original surface (starting point), type and texture of the polishing belts and brushes, and the nature of the polishing process used. Here are the details of the stainless steel finishes that fall into this group based on the table above.
EN 1G-2G - ASTM No. 3 Stainless Steel Finish
This finish is obtained by grinding. The 1G refers to a hot rolled starting point whereas the 2G refers to cold rolled. Due to the process used, the resulting finish provides a rather coarse, unidirectional surface with low reflectivity. The surface roughness can be defined by the manufacturer and agreed with the customer upon request. Most manufacturers define the Ra up to 1 micrometer. Still, it depends on the material and roughness of the grinding belts. The 180 grit and 240 grit ones are the most common.
Generally, common applications of this stainless steel finish are:
- Brewery Equipment
- Food Processing Equipment
- Kitchen Equipment
- Scientific Apparatus
- Indoor Architectural Applications
EN 1J-2J - ASTM No. 4 Stainless Steel Finish
The starting points for these stainless steel finishes are the same as the previous ones. But now the hot rolled or cold rolled steels are processed with polishing belts or brushes. Thus achieving a more refined surface compared to the 1G-2G surfaces. However, the result is still unidirectional and not very reflective. The grade of the brush, polishing belt or surface roughness can be specified by the manufacturer. Typical average roughness is between 0.2-1.0 micrometers, although most manufacturers prefer to stay around 0.4-0.6 micrometers for the 1J – 2J finishes.
Some of the most common applications for the 1J – 2J stainless steel finishes are:
- Architectural Wall Panels
- Beverage Equipment
- Highway Tank Trailers
- Furniture
- Elevator Doors and Interiors
- Sinks
- Sterilisers
EN 1K-2K - ASTM No. 6 Stainless Steel Finish
The starting point is usually hot rolled or cold rolled steel, annealed, pickled and skin passed. Then, finer grit belts and brushes give the steel a satin polish. The 1K – 2K finish provides a smooth reflective surface with an average roughness of 0.5 micrometers or lower, with some manufacturers getting as low as 0.06 micrometers. The stainless steel finish is highly corrosion resistant. Also, you can define additional requirements for adequate corrosion resistance for marine and external architectural applications.
For example, common applications include:
- Exterior Architectural Applications Where Atmospheric Performance is Essential
- Coastal Environments Applications
- Ornamental Applications
EN 1P-2P - ASTM No. 8 Stainless Steel Finish
The same starting point as the 1K – 2K finishes. The last process, in this case, is polishing and buffing with soft cloth mops and special polishing compounds. This helps to achieve a bright polished finish. The 1P – 2P are non-directional, ultra-smooth and highly reflective finishes with a high degree of image clarity in the reflection. Typical Ra values for these stainless steels are below 0.1 micrometers.
Considered the best surface for corrosion resistance, the 1P – 2P stainless steel finishes have many applications. For instance, you may find this type of surface finish used for:
- Column Covers
- Ornamental Trim
- External Wall Panels
- Mirrors
- Reflectors
- Signage
Patterned and Coloured Finishes Explained
Producing patterned stainless steel finishes includes pressing or rolling with patterned rolls. These operations result in an effectively stiffened sheet. As a result, this allows for thinner gauge cladding, a subsequent possible cost saving and overall weight reduction.
The pattern can be applied on one side or on both sides to achieve the 2-sided patterned stainless steels. These are the designations that fall into this group.
EN 2F - ASTM No. 2D Stainless Steel Finish
It usually starts with a 2B or 2R mill finish. So, the common processing involves cold rolling, heat treatment, and skin pass on roughened rolls. Sometimes, bright annealing or annealing and pickling can be performed. The result is a low-reflective stainless steel finish. It is a uniform matt surface on both sides of the sheet. Surface roughness is defined and agreed upon request.
The most common applications for this surface finish include:
- Automotive Exhaust Systems
- Builders’ Hardware
- Chemical Equipment
- Roofing
EN 1M - 2M Stainless Steel Finish
These are the most common 1-sided patterned stainless steels. One side is flat and different textures can be achieved. The design for the pattern is agreed with the manufacturer and mainly depends on the specific application. However, the main idea of the textures is to use them where surfaces are susceptible to accidental knocks and scratches. Therefore, damages are less likely to be noticed.
Also, building entrances use this stainless steel surface finish to avoid accidents caused by slippery floors. Some other popular applications are:
- Building Entrances
- Lift Cages
- Airport Terminals
- Railway Coaches
- Metro Coaches
EN 2W Stainless Steel Finish
These are 2-sided patterned stainless steels in which patterns are rolled or pressed. The process uses male and female rolls and dies. Pattern design is defined upon agreement. The result of the surface on both sides is a corrugated texture, often seen on the factory sheds and construction sites. Subsequently, it increases strength but also offers aesthetic value. The applications are the same as the previous finishes, but with the difference that both sides may be visible.
EN 2L Stainless Steel Finish
This is the designation for all coloured finishes. Colours are agreed between the manufacturer and the customer. A wide range of possibilities exists. The main applications involve mainly decorative or ornamental applications. The color finish can be achieved either by PVD Coating or Heat Treatment processes. Sometimes the coloured finish is also used to match with other materials in complex designs.
Stainless Steel Finishes: The Conclusion
With a wide variety of Stainless Steel Finishes available to choose from, it becomes easier to find the perfect finish for each application. Whether it be Automotive Exhaust or Automotive Grill, or Entrance of the Airport, there is a stainless steel finish to suit it all. We at Raykam deal in all kind of finishes and provide a wide option of PVC covering to protect the finish while transporting and manufacturing. The Stainless Steel Finishes improve the product life cycle and lowers maintainance cost. It makes the product look better, and improve performance too.
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