Many of Marlin’s clients ask if finish or coating “X” is better than finish or coating “Y.” In most cases, the answer will depend on the client’s precise application for the coating or finish.
Recently, one client asked whether a 2B stainless steel surface finish, as specified in ASTM A480, is better than or equal to an electropolished or passivated finish. The answer is that, in most cases, electropolished finishes are superior to the more common 2B finish in terms of performance for stainless steel.
What is a 2B Stainless Steel Finish?
2B is the term used by the ASTM A480 standard to define “a smooth, moderately reflective cold-rolled annealed and pickled or descaled finish typically produced by imparting a final light cold-rolled pass using polished rolls.”
It is the most widely-used stainless steel finish available today. In fact, most of Marlin’s steel wire supply is 2B finish by default.
Some key considerations for this finish include:
- It is the most economical finish by base cost
- 2B is chemically-resistant because of the pickling process—which may enhance the oxide layer
- It has a relatively smooth surface
- There may be variance in appearance between batches—it typically can’t be matched post-production for uniformity of appearance
In many applications, 2B stainless steel surface finishes are perfectly suitable for the task at hand. However, they are often not as effective as electropolished finishes are for mechanical performance.
Why Electropolishing is Generally Superior
While having stainless steel electropolished might be costlier than using the “default” 2B finish produced by most mills, it is often well worth the added cost.
The benefits of electropolishing over using the standard 2B finish include:
- Microscopically Smooth Surfaces. The electropolishing process dissolves the microscopic peaks in the surface of stainless steel—leaving an incredibly smooth, mirror-like finish. This finish is inherently nonstick and free of burrs.
- Reduced Part Fatigue. Many surface-layer micro fissures are eliminated by electropolishing—removing structural weak points that contribute to fatigue on parts. This creates a stronger, longer-lasting wire form.
- Uniform Appearance. Another benefit of the microscopic smoothness of electropolished stainless steel is that getting a uniform appearance is quite simple. Electropolishing strips away many surface contaminants and marks such as weld and burn marks to leave a mirror-like, smooth finish.
Overall, electropolishing produces a smoother, stronger, and more attractive wire form than the standard 2B finish.
When choosing a surface finish for your custom wire forms, it’s important to balance their performance needs thoroughly. This is one reason why Marlin Steel tests every wire basket and tray design used advanced physics simulation software. By testing designs against the projected stresses of the application they’ll be used for, it’s possible to spot performance issues that may otherwise have been forgotten.
So, be sure to consult with an experienced mechanical engineer before settling on a surface finish or coating, just in case.