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Stainless steel polishing is a manufacturing process used to improve the functional and/or aesthetic qualities of a stainless steel surface. During polishing operations, industry professionals employ different methods and equipment to achieve different finishes to suit the intended use case of the part.

Types of Stainless Steel Polishing Finishes

Stainless steel polishing can produce a wide range of finishes, including the following:

#3.This coarse finish—also referred to as a ground, rough, or rough ground finish—generally serves as a preliminary surface finish on a part before it proceeds to further manufacturing and finishing operations. It can be used to deburr or remove excess material that may impact the quality or accuracy of other processes.
#4. A #4 finish—also called a brushed, directional, or satin finish—features finer grit lines that are uniform in appearance and direction. The exact specifications of this finish depend on the industry; for example, #4 dairy or sanitary finishes are much finer than #4 architectural finishes.
#5. A #5 finish features a smooth, satin-like surface.
#6. A #6 finish—also known as a fine satin finish—has softer and less reflective polishing lines than a #4 finish.
#7. In contrast to the previous finishes, a #7 finish is reflective—albeit not clear. This quality is due to the use of higher grit abrasives and sisal buffing techniques.
#8. A #8 finish is highly reflective, warranting its designation as a mirrored finish. Similar to #7 finishes, #8 finishes require abrasive media polishing and sisal buffing, as well as color buffing.

Stainless Steel Polishing Methods

Most stainless steel polishing operations employ abrasive media, such as alumina, ceramics, and zirconia, to achieve the desired finish. The method of polishing differs depending on the finish required. Some of the most common polishing methods include:

Belt grinding or sanding. The belt used in this process is coated in abrasive material that ranges in size, depending on the type of finish needed.
Edge polishing. The edge polishing process is used to improve the edges of a part to reduce the risk of corrosion or contamination.
Face polishing. Similar to belt grinding/sanding, face polishing uses a variety of grit sizes to achieve different finishes. The abrasive used generally consists of zirconia or ceramic material.
Sisal buffing. This process is used to achieve #7 and #8 finishes. It uses buffing wheels made from sisal fibers.
Color buffing. Color buffing is only used when a #8 finish is required. The process uses a buffing wheel to apply a coloring compound to previously smoothed or buffed surfaces, resulting in a mirrored appearance.

Benefits of Stainless Steel Polishing

Compared to unpolished stainless steel parts, polished stainless steel parts have several benefits, including:

Better aesthetics. Polishing makes finished parts and products look more professional and put together. In addition to improving the surface texture, the process removes excess material and imperfections and/or adds a consistent satin or mirrored finish.
Longer product service life. As the stainless steel polishing process improves the surface quality of parts, it reduces the risk of corrosion development. This characteristic increases the durability and longevity of the end product.
Lower risk of contamination. In addition to preventing corrosion, polished finishes prevent contaminants—such as bacteria, chemical compounds, and moisture—from entering, making it easier to clean and maintain the part.

Challenges of Stainless Steel Polishing

Each stainless steel grade has a distinct chemical composition, resulting in different physical and chemical characteristics. As such, it is important to verify whether the grade can withstand polishing before proceeding with full-scale production. Working with a professional metal finishing company is the best way to ensure the use of the right materials and polishing methods.

Some of the other considerations to keep in mind when planning and performing stainless steel polishing operations are:

Stress hardening. Stainless steel is prone to hardening when exposed to high levels of stress, which can make polishing difficult after the material hardness exceeds a certain threshold. Ensuring polishing operations occur rapidly without overworking the materials is key to ensuring the achievement of a proper polished finish.
The surface of stainless steel oxidizes quickly, forming a thin protective layer that resists rust and corrosion. The formation of this layer hinders polishing, so industry professionals must be sure to complete operations before it has a chance to reform.

Applications of Stainless Steel Polishing

Some of the most common stainless steel forms subjected to polishing are those without complex designs and geometries that can impede operations, such as:

Polished parts and products find application in a wide range of industries. In particular, the oil and gas and wastewater treatment industries make use of polished stainless steel parts for their superior resistance to corrosion and contamination.

Centerless Grinding and Polishing Operations

Industry professionals employ centerless grinding to ensure a part maintains precise and tight tolerance specifications. In addition to being used for grinding operations, the process can be used for polishing operations to achieve high-quality and consistent finishes. While it is suitable for grinding and polishing cylindrical parts and products made from stainless steel, it can also accommodate a wide range of materials—including aluminum, hardened steel, and plastic—to a variety of finish levels.

High-Quality Stainless Steel Polishing Services at Stainless Shapes

At Stainless Shapes, we offer polishing services—including belt polishing and centerless grinding—for our stainless steel material to facilitate the delivery of products that meet our customers’ exact needs. We handle centerless grinding requests for parts with diameters ranging from 0.125 inches to 12 inches with a maximum length of 50 feet. For bar and component grinding requests, we accommodate diameters ranging from 0.005 inches to 3 inches depending on length.

The finishes we offer include:

#3 to #8
Non-directional
Longitudinal
Custom

For more information about our stainless steel polishing services, contact us today.

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