How to Specify Electropolishing

Posted by Scott Potter on March 11, 2016

Electropolishing is used to improve surface finish and corrosion resistance, enabling parts to perform better and last longer. While there is no unified standard on how to specify electropolishing, there are some best practices that engineers and manufacturers can use to ensure the final finish on their parts meets their specific requirements.

Most companies do not provide thorough specifications on their drawings. Doing so can ensure optimal performance and a long cycle life. Industries such as aerospace and medical have a tendency to provide more detailed processing information due to the critical nature of their components. 

When specifying electropolishing, there are four main areas to address:specifying_electropolishing_on_a_part_drawing.png

1. Amount of Material to Be Removed and 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. In some cases, the amount that can be removed is very minimal and must stay within prescribed size ranges.

Additionally, indicating the desired finish will determine how much metal needs to be removed to achieve that finish. Microfinish improvement, for example, requires a minimum of .0005” total material removal from a part. Micro-deburring 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. 

2. Fixturing Location and Critical Areas

Identifying the critical areas of the part helps with determining how to fixture the parts correctly. During the electropolishing process, parts are fixtured on custom racks and submerged into an electrolytic bath. The contact location can be adjusted to minimize the marks from fixturing and to prevent any critical areas from being altered during the electropolishing process.

Indicating the critical areas, whether for aesthetics or function, can ensure optimal results from the electropolishing process. 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 as contacting improperly can alter the part’s functionality in its final use. 

If aesthetics are a concern, engineers can identify the critical areas to help prevent fixturing marks from being visible to the end user. This is especially critical in parts used in medical and food applications. To make sure the fixturing location is acceptable, Able highly recommends sending samples for processing and final approval prior to submitting production parts.

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3. Established Company or Industry Specs

Companies that already have process specifications for electropolishing will either use industry specs. or a company specific spec. When requesting a quote from Able, it’s important to provide these standards to ensure that we can meet the spec. And provide the finish that is required. For companies that do not have a specification associated with their part, Able will recommend an industry specification or provide a more detailed spec. that is part specific. The most commonly used electropolishing spec. is ASTM B912. As with most specs., this is not part specific and is intended to be used as a guideline for part processing. It also includes various testing methods for verifying that your part meets the passivation requirements.

4. Packaging Needs

Packaging plays a critical role in the manufacturing process. Since, the electropolishing is often the final step in manufacturing, it is paramount that the parts are properly packaged to maintain the finish prevent damage. Parts incorrectly packaged for shipment can wind up as scrap, which can become quite costly and cause the customer to be late with their order.

Able Electropolishing can recommend many different types of packaging to protect parts. We offer everything from bulk packaging to individual packaging in nitrogen purged, sealed bag performed in a clean bench. Many companies do not send out a lot of work for secondary operations and don’t put much thought into the packaging. Since we have a lot of experience packaging parts of all shapes and sizes, we provide   packaging recommendations when providing our quotations. By indicating the final packaging needs on drawings for electropolished parts, manufacturers can guarantee their parts arrive undamaged and meet customer expectations.

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