Apart from the grade and forms of steel used in a project, the finish is most likely to impact both visual appearance and performance.
In most cases, finish is something you’ll choose at the time of ordering. However, you can also adjust or create a finish yourself with the right equipment and skilled application.
Not sure what finishes are available or how they impact the various facets of stainless steel, such as corrosion resistance or cleanliness? This guide will get you up to speed…
13 Finishes for a Range of Uses
While there are variations of each finish that might be available from a stainless steel supplier or applied after purchasing, most popular finishes fall into one of 13 types.
The first 5 finishes (Numbers 0 through 2BA) are referred to as mill finishes. These are often the finishes in which steel is produced. They may be used as-is or refined further through additional steps depending on the desired appearance.
|Number 0:||Hot-rolled and annealed|
|Number 1:||Hot-rolled, annealed, and passivated|
|Number 2B:||Cold-rolled, annealed, pickled, and passivated, with an additional pass through highly polished rollers|
|Number 2BA:||Features the same processing as 2B, but requires annealing in an oxygen-free vacuum|
|Number 2D:||Cold-rolled, annealed, pickled, and passivated|
Finishes number 3 to 8 apply an increasingly smooth texture to the surface of the steel, with brushed and coarse having a texture that is both visible and noticeable to the touch.
The Number 6 matte finish is rarely used in modern projects, however, it still has a place in restoration or small projects where a unique appearance is desired. Reflective and mirror finishes are the smoothest of the series, providing a glossy, smooth finish with little visual distortion. However, the additional processing required also results in added cost.
The final two finishes (Numbers 9 and 10) refer more to the processes used than the final appearance. Results range from rough to reflective and can even include colour variations and other interesting features designed to increase visual appeal or provide a particular appearance.
|Number 9:||Bead blasted|
|Number 10:||Electropolished or heat-colored surfaces|
Uses for Various Finishes
While each finish had a unique appearance, it also impacts the corrosion resistance and hygienic nature of the steel.
Smoother steels are easier to clean and stand up to chlorides and other corrosion sources well.
Rougher steels are more affordable, but won’t withstand exposure to corrosion sources as well and are tougher to clean.
This is important if you’re considering stainless steel for food preparation or medical environments.
Most food-grade steels start with a minimum finish of 4—though many will use a higher finish on accents or for appliances.
Other common uses by finish number include:
|Number 1:||Air heaters, annealing boxes, boiler baffles, carburizing boxes, crystallizing pans, firebox sheets, furnace arch supports, furnace conveyors, furnace dampers, furnace linings, furnace stacks, gas turbine parts, heat exchanger baffles, heat exchanger tubing supports, incinerators, industrial oven liners, kiln liners, oil burner parts, recuperators, refineries, and tube hangers|
|Number 2B:||Bakeware, chemical plant equipment, dye house equipment, flatware, laundry and dry cleaning, paper mill equipment, pharmaceutical equipment, plumbing fixtures, refrigeration, sewage treatment, sheet metal products, small tanks, solar collector panels, vacuum drum dryers, waste fuel pool liners, and wheel covers|
|Number 2BA:||Appliance trim, appliances, architectural components, auto trim, builder’s hardware, chute liners, commercial refrigerators, cookware, fishing equipment, flatware, food processing equipment, general hardware, highway truck trailers, mass transit cars, radiant heaters, range hoods, scientific apparatus, surgical instruments, and textile finishing equipment|
|Number 2D:||Automotive exhaust systems, builder’s hardware, chemical equipment, chemical trays and pans, electric range parts, furnace parts, petrochemical equipment, railcar parts, roof drainage systems, roofing, and stone anchors|
|Number 3:||Brewery equipment, food processing equipment, kitchen equipment, and scientific apparatus|
|Number 4:||Appliances, architectural wall panels, beverage equipment, boat fittings, bus shelters, clean rooms, column covers, dairy equipment, elevator doors and interiors, escalator trim, food processing equipment, furniture, highway tank trailers, hospital surfaces and equipment, instrument or control panels, kitchen equipment, luggage handling equipment, mass transit equipment, restaurant equipment, sinks, sterilizers, storefronts, and water fountains|
|Number 5:||Most commonly used in architectural elements in coastal environments where a reflective or bright finish is not appropriate|
|Number 7:||Architectural and decor uses such as column covers, ornamental trim, and wall panels|
|Number 8:||Clean rooms, column covers, mirrors, ornamental trim, press plates, reflectors, signage, and wall panels|
As you can see, by adjusting the finish, you can adapt stainless steel to meet a variety of requirements.
Better still, most finishes are applicable to nearly any grade of steel, allowing you to pair the best steel for your uses with the ideal finish to amplify its traits further.
Applying a Finish to Stainless Steel
In most cases, applying a finish is something that is done either by the supplier or through an experienced service provider.
This is particularly true for finishes 9 and 10 as they require specialized equipment, chemistry, and knowledge to achieve the desired results.
However, the basics of finishing steel are similar across most other types. All finishes start by applying an abrasive to the surface of the steel.
In most cases, you will start with a higher grit abrasive to set the overall finish and then use additional cycles at decreasing grits to hone the finish.
Abrasives can take a variety of forms, including:
- Aluminum oxide powders
- Zirconium powders
- Ceramic powders
Tools are equally varied, including:
- Wraparound pipe sanders
- Finger belt sanders
- Pipe and linear finishers
- Flap wheels
Each abrasive and tool brings its own set of considerations and ideal uses.
While smaller tools are great for tight corners or detailed work, they won’t work for large surfaces. Pipe sanders, while great for cylindrical surfaces, won’t achieve the desired result on flat surfaces.
There may also be chemicals involved to both impact change on the finish itself or lubricate surfaces throughout the finishing process.
While exact requirements, tools, and approaches will vary based on your intended outcome and usages, there are a few rules universal to finishing:
- Finish pipes and other cylindrical pieces in a circumferential alignment around the body of the pipe, not along the length of the pipe.
- Finish flat parts and surfaces in the same direction on all sides for a seamless appearance
- Start with a higher grit and reduce grit through each pass of the finishing process until you reach your intended result
- Work in small sections, blending each section together as you. In most cases, attempting to finish the entire surface of a part will create an uneven finish and subpar results.
- Be sure to check any requirements regarding chemicals if you plan to use the steel in sensitive environments—such as food service or medical facilities.
Disclaimer: This guide is intended as an overview of stainless steel finishing. Before attempting to apply finishing to stainless steel yourself, consult any safety guidelines regarding both the equipment and chemistry involved to minimize risk to personnel, equipment, and materials.
While finishing stainless steel comes with increased time requirements and cost, its ability to both improve the visual appeal of stainless steel and further enhance its corrosion resistance make it a powerful tool for getting the most out of your stainless steel investment. If you’d like more information on finishing processes, pre-finished stainless steel products, or proper finishes for your intended application, the experts at Unified Alloys are ready to assist you. With more than 40 years of experience serving some of North America’s largest industries, we have the expertise needed to help you find the ideal solution for your needs.