Top-quality electropolishing should combine both reflectivity and long-lasting appeal, with a smooth surface. Surfaces that are smoother upon undergoing electropolishing tend to experience better results from the process.
High-quality electropolishing will be devoid of flaws such as:
- Streaks and stains
- Orange peel
- Water spots
- Irregular patterns
- Pebbly or pitted surfaces
When magnified, the surface should ultimately show no signs of flaws and remain virtually featureless.
What Culminates in Good Electropolishing Results?
To achieve the best results following electropolishing, the surface of the materials should have superior properties, along with the appropriate conditions and techniques to get the job done right.
On the other hand, there is no guarantee that the results will turn out the way you want, such as in cases where a stainless steel part made using a certain type of alloy or with a history of heavy use.
Any results that leave an overall unfinished appearance are likely due to the original quality of the material itself, and may not be correctable.
Effects such as pits, dull or grainy luster, and exposed seams could all come from past issues from treatments, including inappropriate temperature during cold rolling, hot-rolling of slabs, over- or under-pickling or annealing, excessive grinding before undergoing cold-rolling, or contamination to certain elements such as industrial process materials, lubricants, and pollutants, along with other potential damage.
Stainless steel grades, including Types 303 and 416, are also likely to experience frosting after the process as electropolishing removes sulfide inclusions.
Ultimately, the best results will be seen with fine, uniform crystal homogeneous structures.
During the electropolishing process, Hastelloy parts are submerged in an electrochemical bath that removes a controlled, uniform layer of surface metal. This will strip away any imperfections and improves the Ra finish by as much as 50%.
How to Determine if Electropolishing Results are Good
Learning to distinguish good from bad electropolishing is similar to identifying counterfeit money. You need to understand what the real thing looks like, how it performs, and how it feels following the process. Poor electropolishing will then stand out for its flaws upon examining finished parts.
Electropolishing is favored among many different businesses because of the quality of the final finish when performed the right way.
The process should enhance the surface, offer contamination resistance, be non-sticking, and be non-particulating. In short, for the best cosmetic finish, electropolishing is the go-to finishing process in many cases.
One example of a surface that could appear electropolished to the untrained eye is a bugged surface, such as one with a No. 8 finish.
This type of surface can even yield the same Ra or RMS profilometer readings, but closer inspection via photomicrographs will be able to help identify the differences between the two. While the electropolished surface would look smooth and nearly flawless, the buffed surface would look damaged, disturbed, and smeared.
With the help of photomicroscopy and sufficient training, experts can determine whether the results following electropolishing are good or bad.
In the end, electropolishing is one of the best processes for a wide variety of alloys, including an array of stainless steels.