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Preparing Parts for Electropolishing Cheat Sheet by

12 Steps for Preparing Parts for Electropolishing
steps     parts     electropolishing     preparing

Introd­uction

When sending in parts for electr­opo­lis­hing, it is crucial for the parts to be correctly prepared for the process. Since electr­opo­lishing is typically the last step in the manufa­cturing process, proper prepar­ation of parts is crucial for optimal results.

1. Remove Surface Scratches

Electr­opo­lishing will highlight, rather than remove scratches and machine lines. The general rule of thumb is if you can feel the scratch or machining defect with your thumbnail, electr­opo­lishing will not remove it. Electr­opo­lishing removes only a very thin surface layer, and deeper scratches remain visible if not removed prior to the process. For a smooth, high-shine surface finish, machining lines and deeper scratches should be removed by mechanical polishing or other means prior to electr­opo­lis­hing.

2. Remove Macro Burrs

Large burrs should be removed with finishing methods such as vibratory finishing or tumbling. In some cases, it is not the height of the burrs, but the width of burrs, that determines whether they will be totally removed with electr­opo­lis­hing. We suggest submitting samples to confirm effect­iveness prior to sending production lots.

3. Remove Traces of Soap Lubricants

Prior to submitting a part for electr­opo­lis­hing, if you have used soap-based lubric­ants, remove all traces of the product, or notify your electr­opo­lisher prior to submitting parts. Soap products contain silicates that cling to the metal, and if not removed can lead to resist patterns (unpol­ished areas) or stains in the finished part.

4. Remove Adhesives and Coatings

Certain types of prefin­ished stainless steel are purchased with vinyl coatings that are adhered with a clear adhesive. After peeling off the vinyl these adhesives must be removed prior to electr­opo­lis­hing. The standard pre-cl­eaning method of vapor degreasing will not remove the adhesive. Altern­ative pre-cl­eaning methods are necessary and can be easily implem­ented if we are aware of the situation. Leaving the adhesive on the parts will cause resist patterns, creating an uneven finish that would need to be removed mechan­ically

5. Understand Your Desired Microf­inish (Ra) Value

When removing .001” material total (.0005” per surface), electr­opo­lishing can reduce the Ra value of a part by up to 50%. For example, a part with an initial Ra value of 16 can be improved to a final Ra value of 8 after electr­opo­lis­hing. Determ­ining your desired, final Ra is important and will dictate how you prepare your part for electr­opo­lis­hing. Lowering the Ra finish may require adding a secondary finishing operation after machining such as grinding or mechanical polishing prior to electr­opo­lis­hing.
 

6. Ensure Welds Are Airtight & Uniform

All welds must be airtight, with no pinholes where the electr­olyte and other fluids could become entrapped. Once entrapped, these fluids can be difficult to remove, and can continue to leech out of the part when in use.

7. Clean from Welds

Prior to electr­opo­lis­hing, remove the excessive black or char from welded areas. Lubricants and oils can be burned into the metal during the welding process, and care is necessary to prevent this condition. Once lubricants and oils are burned into the part it can be difficult to remove, and can affect the quality and appearance of a part after electr­opo­lis­hing.

8. Eliminate Advanced Scale from Heat Treating

For parts that have been heat-t­reated, advanced scale must be removed before electr­opo­lis­hing. The scale left from heat treating acts as an insulator and reduces overall conduc­tivity, creating unwanted resist patterns on the part. Have all advanced scale from heat-t­reating fully removed prior to submitting a part for electr­opo­lishing for uniform, shiny results.

9. Make Drain Holes Round/­Square Tubing Parts

We recommend adding drain holes on weldments made with butt welded tubing where the ends are covered. Drain holes should be designed into the part and included in part drawings. The drain holes are effective for removing entrapped electr­olyte and other liquids from the interior of the part.

10. Ensure Blasted Parts Have a Uniform Surface

To correctly prepare a part that has to undergo blasting, be sure to use uniform pressure to create a uniform imping­ement depth in the metal. The blasting may look uniform on the surface but after removing the outer skin with electr­opo­lis­hing, “hot and cold spots” will be evident upon comple­tion. . A blasted part with an uneven surface will have bright and dull areas.

11. Choose High Quality Wire for Wire Parts

For springs, racks, and other parts made from stainless steel wire, specify EPQ (elect­rop­oli­shing quality) wire. EPQ wire has a smoother, brighter finish and yields a chrome­-like appear­ance. . Using lower quality wire can result in parts that have a lacklu­ster, frosty finish.

12. Specify 2B Finish on Sheet Metal

For sheet metal compon­ents, we recommend specifying a 2B finish to receive a bright, uniform finish after electr­opo­lis­hing. If a mirror­-like finish is required, you will need to purchase a bright­-an­nealed material.

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