Specifying Electropolishing
4 Steps & Best Practices
Electropolishing is used to improve surface finish and enhance corrosion resistance, enabling critical metal parts to perform better and last longer. Below are best practices in four steps for engineers and manufacturers to use in providing electropolishing specifications for your part requirements:
1. Material Removal & Desired Surface Finish
Before submitting a part to be electropolished, engineers need to have an idea of how much of the surface material can be removed without impacting the part’s intended function. This will vary depending on the application of the part itself, the part-specific size tolerances and the alloy. In some cases, the amount that can be removed is very minimal (.0001” per surface) and must stay within prescribed size ranges.
The Able Electropolishing process includes the ability to control tolerances up to +/- .0001” per surface.
Specifications should also include the desired part finish so that we can also tailor material removal based on the application and part-specific requirements, with a controlled, flexible process that ensures that the surface finish adheres precisely to the results you are seeking.
Microfinish improvement, for example, requires a minimum of .00025” per surface total material removal from a part. Microdeburring may require more removal. Both the desired amount of surface material to be removed and the ideal surface finish should be included when specifying the electropolishing process on a drawing.
Examples of material removal specifications by application include:
Metal Alloy | Material Removal Control in the Process | Minimum / Cleaning | Microfinish | Microdeburring | Corrosion Resistance |
| Titanium | .0001″ per surface | .0001″ per surface | .00025″ per surface | .0005″ per surface | N/A |
| Nitinol | .0001″ per surface | .0001″ per surface | .00025″ per surface | .0005″ per surface | N/A |
| Brass | .00025″ per surface | .00025″ per surface | .0005″-.001″ per surface | .0005″ – .001″ per surface | N/A |
| Copper | .00025″ per surface | .00025″ per surface | .0005″-.001″ per surface | .0005″ – .001″ per surface | N/A |
| Steel | .00025″ per surface | .00025″ per surface | .0005″-.001″ per surface | .0005″ – .001″ per surface | N/A |
| Stainless Steel | .0001″ per surface | .0001″ per surface | .0005″ per surface | .0005″-.001″ per surface | .0005″ per surface |
| Aluminum | .00025″ per surface | .00025″ per surface | .0005″-.001″ per surface | .0005″ – .001″ per surface | N/A |
2. Fixturing Location & Critical Areas
Identifying the critical areas of the part helps determine how to fixture the parts correctly. During the electropolishing process, parts are fixtured on custom racks and submerged into an electrolytic bath.
Some parts, especially when it comes to parts that need to retain a sharp edge, require extra care when it comes to the fixturing positioning. For example, parts that need to retain a sharp edge can be fixtured to ensure optimal results for part functionality.
If aesthetics are key, engineers can identify the critical areas to help prevent visible fixturing witness marks. In addition to establishing other key parameters, Able’s sample electropolishing process can also help determine the most effective location for fixturing.
3. Established Company or Industry Specs
Companies that already have process specifications for electropolishing will either use industry or company-specific specifications. These standards should be included when requesting a quote to ensure that Able can meet the specification and provide the required finishing results. ASTM B912 is the most commonly used electropolishing specification. Like most specifications, this is not part specific but is used as a guideline for part processing.
4. Packaging Needs
Packaging plays a critical role in protecting the finish of your parts.
The Able Electropolishing team has decades of expertise in providing the highest quality finishing results from start to finish and can provide consultation around the best packaging for your parts. Our process is built around a “Finish First” approach in which the end results – including packaging – are factored into specifications as early as the prototyping stage. By indicating the final packaging needs on drawings for electropolished parts, manufacturers can guarantee their parts arrive undamaged and meet customer expectations.
AES-01
Parts are precleaned and electropolished to a specific material removal defined during the sample process. Material removal is verified using a digital micrometer using ANSI/ASQ Z1.4 inspection Level S-3 from a consistent location(s) on the part. Parts are rinsed using D.I. water with ultrasonics, dried, inspected and then packed.
AES-02
Parts are precleaned and electropolished to a specific material removal defined during sample process. Material removal is verified in process using a digital micrometer using ANSI/ASQ Z1.4 inspection Level S-3. In addition, specified surfaces are validated using a profilometer to ensure Ra is achieved as noted on the print. Parts are rinsed using D.I. water with ultrasonics, dried, inspected and then packed.
AES-03
Parts are precleaned and electropolished to achieve a uniform luster and brightness defined during the sample process. Material removal and surface finish are not measured which makes this a more cost effective option for applications with less stringent requirements and part specific tolerances. Inspection is based on a purely visual criteria based on the customer approved Quality Samples. Parts are rinsed using D.I. water with ultrasonics, dried, inspected and then packed.
Note: Rack location for all parts is reviewed during the sample process. A “witness mark” from the tooling making electrical contact with the part will be present after electropolishing and must be considered/evaluated in advance of running production parts. Feedback is required during the sample process to define critical surfaces that should be avoided for fixturing.
Additional Testing:
Able also provides copper sulfate, water immersion, and ferroxyl testing. Able partners with leading labs to perform the following testing:
- Passivation layer thickness per SEMI F72 using Auger Electron Depth Profiling
- Surface Contamination SEMI F73 with high resolution photos before & after electropolishing
- Surface Roughness per SEMI F37 using non-contact, high resolution surface imaging
- Chromium Enrichment SEMI F60 using ESCA (XPS) depth profiling
- Salt Spray Testing to determine corrosion resistance before and after electropolishing
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