Finishing stainless steel protects surfaces and produces a mirror-like shine or matte sheen. You can choose from various stainless steel finishing methods to achieve different looks and functional designs. Combine the right technique with finishing best practices to achieve a look and design that meets your surfacing needs and specs.
8 Techniques for Finishing Stainless Steel
Stainless steel finishing techniques include methods that rely on abrasion, polishing, electrochemical processing, and chemical treatment. Some of today’s top methods are:
- Sandblasting (abrasive blasting)
- Belt polishing (belt grinding)
- Centerless ground finishing
- Electropolishing
- Black oxide finishing (blackening)
- Passivation (chemical cleaning)
- Commercial cleaning and capping
- Thermocouple cleaning and capping
Each of these methods achieves distinct results suitable for different applications.
1. Sandblasting (Abrasive Blasting)
Sandblasting and other methods of abrasive blasting use pressurized fluids or centrifugal force to propel materials against surfaces and erode them for a desired finish. Typically, abrasive blasting produces a dull, matte look, although some methods can produce a softer, brighter surface. Media used for abrasive blasting include steel shot, silicon carbide, and glass beads. Abrasive blasting can serve to prepare a surface for painting, remove rust and stains, or remove a previous finish.
2. Belt Polishing (Belt Grinding)
Belt polishing runs a belt coated in an abrasive substance over a surface to finish it. It produces a high luster suitable for ornamenting surfaces of objects such as appliances. Other applications include deburring and stock removal. You can select different grit levels to control the amount of material removed and the degree of smoothness and shine achieved. Medium grit levels yield a moderately smooth surface and shine, while finer grit levels increase smoothness and luster.
3. Centerless Ground Finishing
Centerless grinding secures a workpiece between rotary grinding wheels rather than using a central spindle or fixture. The wheels can rotate at varying speeds relative to each other to control grinding rate. This allows fine control of smoothness level, refinement of tolerance, or correction of dimensional defects. Centerless grinding yields a finish similar to belt polishing but with visible scratch marks. It can serve applications such as shafts, fasteners, and threaded rods.
4. Electropolishing
Electropolishing reverses electroplating, using an electrolyte bath and electrical current to produce controlled oxidation and strip the outer layer from a workpiece. This leaves an even, shiny, uncontaminated surface. Electropolishing can be used for polishing, deburring, or passivation. It can produce a bright finish or a sterile surface.
5. Black Oxide Finishing (Blackening)
Black oxide finishing uses a heated chemical solution to convert the surface of stainless steel into a magnetite coating. This reduces light reflection and moderately improves corrosion resistance. It leaves a matte appearance that can enhance visual appeal or reduce glare. Black oxide finishing can be used for applications such as aerospace gears, fasteners, and hydraulic components.
6. Passivation (Chemical Cleaning)
Passivation uses nitric or citric acid to remove free iron from a stainless steel surface, producing an oxide shield. This promotes steel’s corrosion resistance and prevents embedded particles from causing discoloration, rust, or pitting. Nitric acid works best for dissolving iron particles without affecting stainless steel. To ensure the removal of particles, passivation should be performed last after any other mechanical, welding, or high-temperature procedures and before coating or assembly.
7. Commercial Cleaning and Capping
For maintenance, some stainless steel tube applications require a specialized cleaning and preparation process to improve finish, remove contamination, and meet regulatory compliance. Caps seal the ends of the tubes to exclude impurities.
8. Thermocouple Cleaning and Capping
Thermocouple cleaning and capping maintenance procedures are similar to commercial cleaning and capping. They remove and prevent contaminants that can affect temperature sensors.
5 Stainless Steel Finishing Best Practices
For optimal results, stainless steel finishing techniques should be applied following best practices. To get better results:
- Select your finishing technique based on your application
- Prepare surfaces properly
- Choose the right abrasives
- Polish properly for a mirror-like finish
- Follow maintenance best practices
Here are some brief tips for implementing these guidelines:
1. Select Your Finishing Technique Based on Your Application
Different finishing techniques achieve different functional and aesthetic effects. Specifying the results you want can help you select the best technique to achieve your goals. Consider whether the end use you envision imposes requirements such as fine control over surface shaping, enhanced corrosion resistance, high luster, or low glare. Refine your specs by learning to measure surface finish using metrics such as roughness average (RA) or roughness measurement system (RMS).
2. Prepare Surfaces Properly
Stainless steel surfaces should be properly prepared before finishing. Complex parts should be disassembled into their components to ensure total surface coverage. Plating and painting should be stripped to expose target surfaces and remove excess particles.
3. Choose the Right Abrasives
Selecting the right abrasive makes deburring more efficient. Top abrasives for cutting stainless steel include aluminum oxide, silicon carbide, zirconia, and ceramic. Aluminum oxide trades off low cost for short durability. Silicon carbide is harder and sharper but more costly than aluminum oxide. Zirconia’s tough durability makes it suitable for heavy grinding. Ceramics provide a hard, sharp surface with long durability at a premium price.
4. Polish Properly for a Mirror-like Finish
If you’re going for a shiny, mirror-like look, you’ll generally get the best results using belt polishing. Level and sand your surface before polishing it. Use fine grit to remove fine scratches and coarse grit to remove larger ones.
5. Follow Maintenance Best Practices
To maintain aesthetic and hygienic qualities, stainless steel needs proper maintenance. Schedule maintenance one to four times a year for standard applications and daily maintenance for uses requiring exceptional hygiene or corrosion protection. For routine applications, soap or a mild detergent with warm water followed by rinsing suffice. Specialized cleaning methods can be used for treating issues such as fingerprints, rust, or lime deposits. Passivation can be used to remove free iron.
Contact the Stainless Steel Professionals at Eagle Stainless
Looking to enhance the finish of stainless steel for your project? Look no further! Contact the expert team at Eagle Stainless Tube & Fabrication Inc. today. With our expertise in finishing stainless steel, we can help improve your part’s aesthetic and function. Trust our commitment to excellence, quality, and customer satisfaction for all your fabrication needs. Contact us today to learn more!